Subject: Re: (No subject) From: "rem11560@............ rem11560@netzero.com Date: Thu, 1 Jul 2004 01:40:59 GMT Hi Jason, I have some suggestions. Others please feel free to disagree. 1. Greatly reduce the mass of the pendulum. A mass of 5 pounds is probably too much for your superstructure. As the pendulum moves, it exerts a transverse moment on the support structure and baseplate, making it hard to achieve a stable long period. High mass also makes shunt resistance damping practically impossible. 2. Stiffen the superstructure laterally with cross bracing. 3. Having a magnet on the pendulum makes the sensor responsive to stray magnetic fields. Put the coil on the pendulum and the magnet on the base. While you are at it, place a second magnet on the opposite side of the coil, with poles reversed. You will get twice as much sensitivity, much better linearity of response, and half as much shunt conductance required for a given damping level. With the coil mounted on the pendulum, you might not need any extra mass, and that would make shunt damping easier as well. 4. Be sure to use a cover which shields the sensor from ambient temperature change and drafts. You may need a heater inside at the top to prevent convection of air upward from the baseplate. 5. Put a one microfarad capacitor across the input terminals of your amplifier. I have amplifiers of differing designs, and they all oscillate internally if there is no shunt capacitance across the input terminals when the source is inductive (i.e., a sensor coil). You cannot see this oscillation at the output terminals; it manifests itself as excess output noise, and in the case of my DC amplifiers, a large and fluctuating bias. If you want to see my sensors, visit John Lahr's web site at the pages he kindly provides for my amateur efforts: http://www.jclahr.com/science/psn/mcclure/ Regards, Bob McClure Locust Valley, NY ________________________________________________________________ The best thing to hit the Internet in years - NetZero HiSpeed! Surf the Web up to FIVE TIMES FASTER! Only $14.95/ month -visit www.netzero.com to sign up today! __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: (No subject) From: "Larry Cochrane" lcochrane@.............. Date: Wed, 30 Jun 2004 21:30:41 -0700 > 5. Put a one microfarad capacitor across the input terminals of your amplifier. I have amplifiers >of differing designs, and they all oscillate internally if there is no shunt capacitance across >the input terminals when the source is inductive (i.e., a sensor coil). You cannot see this >oscillation at the output terminals; it manifests itself as excess output noise, and in the >case of my DC amplifiers, a large and fluctuating bias. I question this one... I have never seen a need to place a cap on the input of an op-amp to stop internal oscillations. If you are getting some RF into the input you can place a .01 ceramic cap across the input to shunt out the RF before it gets into the op-amp. I have seen oscillation problems with op-amps driving large capacitance or inductive loads. -Larry Cochrane Redwood City, PSN __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Your seismometer From: Jason Brady jr_brady@........... Date: Thu, 01 Jul 2004 19:09:28 -0700 Hello Bob, Thanks for taking the time to provide feedback. Please see my responses/questions below. Jason At 06:47 PM 06/30/2004, you wrote: >Hi Jason, > > I have some suggestions. Others please feel free to disagree. > >1. Greatly reduce the mass of the pendulum. A mass of 5 pounds is probably >too much for your superstructure. As the pendulum moves, it exerts a >transverse moment on the support structure and baseplate, making it hard >to achieve a stable long period. High mass also makes shunt resistance >damping practically impossible. How much weight is preferable--is there a rule of thumb (or better yet, mathematical formulas) based on the boom size and/or other parameters? >2. Stiffen the superstructure laterally with cross bracing. It seems pretty sturdy but I can easily add another cross-brace. >3. Having a magnet on the pendulum makes the sensor responsive to stray >magnetic fields. Put the coil on the pendulum and the magnet on the base. >While you are at it, place a second magnet on the opposite side of the >coil, with poles reversed. You will get twice as much sensitivity, much >better linearity of response, and half as much shunt conductance required >for a given damping level. With the coil mounted on the pendulum, you >might not need any extra mass, and that would make shunt damping easier as >well. Easy enough, but where should I run the wires? Along the boom or up the suspension? >4. Be sure to use a cover which shields the sensor from ambient >temperature change and drafts. You may need a heater inside at the top to >prevent convection of air upward from the baseplate. Will make an enclosure of Celotex. How about a small appliance lamp instead? >5. Put a one microfarad capacitor across the input terminals of your >amplifier. I have amplifiers of differing designs, and they all oscillate >internally if there is no shunt capacitance across the input terminals >when the source is inductive (i.e., a sensor coil). You cannot see this >oscillation at the output terminals; it manifests itself as excess output >noise, and in the case of my DC amplifiers, a large and fluctuating bias. In parallel with the damping resistor? > If you want to see my sensors, visit John Lahr's web site at the pages > he kindly provides for my amateur efforts: > > http://www.jclahr.com/science/psn/mcclure/ > >Regards, >Bob McClure >Locust Valley, NY Hello Bob,

Thanks for taking the time to provide feedback.  Please see my responses/questions below.

Jason

At 06:47 PM 06/30/2004, you wrote:
Hi Jason,

  I have some suggestions. Others please feel free to disagree.

1. Greatly reduce the mass of the pendulum. A mass of 5 pounds is probably too much for your superstructure. As the pendulum moves, it exerts a transverse moment on the support structure and baseplate, making it hard to achieve a stable long period. High mass also makes shunt resistance damping practically impossible.

How much weight is preferable--is there a rule of thumb (or better yet, mathematical formulas) based on the boom size and/or other parameters? 

2. Stiffen the superstructure laterally with cross bracing.

It seems pretty sturdy but I can easily add another cross-brace.

3. Having a magnet on the pendulum makes the sensor responsive to stray magnetic fields. Put the coil on the pendulum and the magnet on the base. While you are at it, place a second magnet on the opposite side of the coil, with poles reversed. You will get twice as much sensitivity, much better linearity of response, and half as much shunt conductance required for a given damping level. With the coil mounted on the pendulum, you might not need any extra mass, and that would make shunt damping easier as well.

Easy enough, but where should I run the wires?  Along the boom or up the suspension?

4. Be sure to use a cover which shields the sensor from ambient temperature change and drafts. You may need a heater inside at the top to prevent convection of air upward from the baseplate.

Will make an enclosure of Celotex.  How about a small appliance lamp instead?

5. Put a one microfarad capacitor across the input terminals of your amplifier. I have amplifiers of differing designs, and they all oscillate internally if there is no shunt capacitance across the input terminals when the source is inductive (i.e., a sensor coil). You cannot see this oscillation at the output terminals; it manifests itself as excess output noise, and in the case of my DC amplifiers, a large and fluctuating bias.

In parallel with the damping resistor?

  If you want to see my sensors, visit John Lahr's web site at the pages he kindly provides for my amateur efforts:

     http://www.jclahr.com/science/psn/mcclure/

Regards,
Bob McClure
Locust Valley, NY
Subject: Re: Your Seismometer From: "rem11560@............ rem11560@netzero.com Date: Sat, 3 Jul 2004 01:50:21 GMT Hi Jason, Here are my answers to your questions, to the best of my ability to answer them >>1. Greatly reduce the mass of the pendulum. >How much weight is preferable--is there a rule of thumb (or better yet, mathematical formulas) based on the boom size and/or other parameters? Answer: There is no theoretical lower limit on mass, except a quantum one. You could't reduce the mass enough for that to have any effect. The practical limits are susceptibility to air currents, friction in the upper and lower pivots, and over damping caused by the input impedance of the amplifier. Sensors do not have to drive styluses over smoked paper any more. >>2. Stiffen the superstructure laterally with cross bracing. >It seems pretty sturdy but I can easily add another cross-brace. Answer: Just make sure that you have at least one diagonal member. >>3. Having a magnet on the pendulum makes the sensor responsive to stray magnetic fields. Put the coil on the pendulum and the magnet on the base. >Easy enough, but where should I run the wires? Along the boom or up the suspension? Answer: I run my wires down the boom, and let them dangle in a loose coil on the way to a terminal block. >>4. Be sure to use a cover which shields the sensor from ambient temperature change and drafts. You may need a heater inside at the top to prevent convection of air upward from the baseplate. >Will make an enclosure of Celotex. How about a small appliance lamp instead? Answer: Others with experience with large Lehman sensors could answer this with more authority. I would think a small appliance lamp would be OK. >>5. Put a one microfarad capacitor across the input terminals of your amplifier. >In parallel with the damping resistor? Answer: Yes, at the amplifier terminals. Larry Cochrane doubts the necessity of this, but I am using one of his amplifiers, and it was certainly necessary for me. Regards, Bob ________________________________________________________________ The best thing to hit the Internet in years - NetZero HiSpeed! Surf the Web up to FIVE TIMES FASTER! Only $14.95/ month -visit www.netzero.com to sign up today! __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Emon7.2 From: "Alby Judge" martinobs@.............. Date: Sat, 3 Jul 2004 21:31:48 +0800 Does anyone have a copy of Emon 7.2 with support for the Axiom AX-5210 = A/D board that they could send me please. Thanks, Alby, Martin Observatory, Western Australia.
Does anyone have a copy of Emon 7.2 = with support=20 for the Axiom AX-5210 A/D board that they could send me = please.
Thanks,
Alby,
Martin Observatory, Western=20 Australia.
Subject: RE: Emon7.2 From: "Bob Shannon" earth@........... Date: Sat, 3 Jul 2004 07:19:27 -0700 Sorry I do not.but I am sure others will have..Your message gave me pause for thought. Does anyone have a DOS version of Seismic? Alan no longer supports it and did send me a Copy snail mail about 9 years ago..but I hesitate to bother him for a third time. I am setting up a 486 with DOS 6.11 the unbugged version, in order to use as a fast machine for My own Point EQ locator program.the one I wrote in BASIC and compiled back in 1992.Thanks Bob Shannon Pinpoint -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Alby Judge Sent: Saturday, July 03, 2004 6:32 AM To: PSN-L@.............. Subject: Emon7.2 Does anyone have a copy of Emon 7.2 with support for the Axiom AX-5210 A/D board that they could send me please. Thanks, Alby, Martin Observatory, Western Australia.

Sorry I do not…but I am sure = others will have….Your message gave me pause for thought.
Does anyone have a DOS version of Seismic? Alan no longer supports it = and did send me a

Copy snail mail about 9 years = ago….but I hesitate to bother him for a third time.

  I am setting up a 486 with DOS 6.11 the unbugged version, in order to use as a fast machine = for

My own Point EQ locator = program…the one I wrote in BASIC and compiled back in = 1992…Thanks

Bob = Shannon

Pinpoint

 

-----Original = Message-----
From: = psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Alby Judge
Sent: Saturday, July 03, = 2004 6:32 AM
To: = PSN-L@..............
Subject: = Emon7.2

 

Does anyone have a copy of = Emon 7.2 with support for the Axiom AX-5210 A/D board that they could send me = please.

Thanks,

Alby,

Martin Observatory, Western Australia.

Subject: RE: Emon7.2 From: "Steve Hammond" shammon1@............. Date: Sat, 3 Jul 2004 11:48:19 -0700 In a side note I sent EMON 7.0 that I had. I see it has EMON 6.2 opt file the supports the Axiom. Ted sent me a lot of his software to test. Caution. From time to time, there were a few bugs. Regards, Steve Hammond PSN San Jose. -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@................. Behalf Of Alby Judge Sent: Saturday, July 03, 2004 6:32 AM To: PSN-L@.............. Subject: Emon7.2 Does anyone have a copy of Emon 7.2 with support for the Axiom AX-5210 A/D board that they could send me please. Thanks, Alby, Martin Observatory, Western Australia.
In a=20 side note I sent EMON 7.0 that I had. I see it has EMON 6.2 opt file the = supports the Axiom. Ted sent me a lot of his software to test. Caution. = From=20 time to time, there were a few bugs.
Regards, Steve Hammond PSN San Jose.
-----Original Message-----
From: = psn-l-request@................. [mailto:psn-l-request@...............On Behalf Of Alby=20 Judge
Sent: Saturday, July 03, 2004 6:32 AM
To:=20 PSN-L@..............
Subject: Emon7.2

Does anyone have a copy of Emon 7.2 = with support=20 for the Axiom AX-5210 A/D board that they could send me = please.
Thanks,
Alby,
Martin Observatory, Western=20 Australia.
Subject: RE: Emon7.2 From: "Steve Hammond" shammon1@............. Date: Sat, 3 Jul 2004 11:48:19 -0700 In a side note I sent EMON 7.0 that I had. I see it has EMON 6.2 opt file the supports the Axiom. Ted sent me a lot of his software to test. Caution. From time to time, there were a few bugs. Regards, Steve Hammond PSN San Jose. -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@................. Behalf Of Alby Judge Sent: Saturday, July 03, 2004 6:32 AM To: PSN-L@.............. Subject: Emon7.2 Does anyone have a copy of Emon 7.2 with support for the Axiom AX-5210 A/D board that they could send me please. Thanks, Alby, Martin Observatory, Western Australia.
In a=20 side note I sent EMON 7.0 that I had. I see it has EMON 6.2 opt file the = supports the Axiom. Ted sent me a lot of his software to test. Caution. = From=20 time to time, there were a few bugs.
Regards, Steve Hammond PSN San Jose.
-----Original Message-----
From: = psn-l-request@................. [mailto:psn-l-request@...............On Behalf Of Alby=20 Judge
Sent: Saturday, July 03, 2004 6:32 AM
To:=20 PSN-L@..............
Subject: Emon7.2

Does anyone have a copy of Emon 7.2 = with support=20 for the Axiom AX-5210 A/D board that they could send me = please.
Thanks,
Alby,
Martin Observatory, Western=20 Australia.
Subject: RE: Emon7.2 From: "Steve Hammond" shammon1@............. Date: Sat, 3 Jul 2004 11:57:50 -0700 Hi Bob, in a side note I have sent you the Seismic II zip you requested. My version is from 1993... I tested it and it still works. Regards, Steve Hammond PSN San Jose, Aptos CA -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@................. Behalf Of Bob Shannon Sent: Saturday, July 03, 2004 7:19 AM To: psn-l@.............. Subject: RE: Emon7.2 Sorry I do not.but I am sure others will have..Your message gave me pause for thought. Does anyone have a DOS version of Seismic? Alan no longer supports it and did send me a Copy snail mail about 9 years ago..but I hesitate to bother him for a third time. I am setting up a 486 with DOS 6.11 the unbugged version, in order to use as a fast machine for My own Point EQ locator program.the one I wrote in BASIC and compiled back in 1992.Thanks Bob Shannon Pinpoint -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Alby Judge Sent: Saturday, July 03, 2004 6:32 AM To: PSN-L@.............. Subject: Emon7.2 Does anyone have a copy of Emon 7.2 with support for the Axiom AX-5210 A/D board that they could send me please. Thanks, Alby, Martin Observatory, Western Australia.
Hi=20 Bob, in a side note I have sent you the Seismic II zip you requested. My = version=20 is from 1993... I tested it and it still works.
Regards, Steve Hammond
PSN=20 San Jose, Aptos CA
-----Original Message-----
From: = psn-l-request@................. [mailto:psn-l-request@...............On Behalf Of Bob=20 Shannon
Sent: Saturday, July 03, 2004 7:19 AM
To:=20 psn-l@..............
Subject: RE: = Emon7.2

Sorry I do = not…but I=20 am sure others will have….Your message gave me pause for = thought.
Does=20 anyone have a DOS version of Seismic? Alan no longer supports it and = did send=20 me a

Copy snail = mail about=20 9 years ago….but I hesitate to bother him for a third=20 time.

  I am setting up a 486 with = DOS 6.11=20 the unbugged version, in order to use as a = fast=20 machine for

My own = Point EQ=20 locator program…the one I wrote in BASIC and compiled back in=20 1992…Thanks

Bob=20 Shannon

Pinpoint

 

-----Original=20 Message-----
From:=20 psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of Alby = Judge
Sent: Saturday, July 03, 2004 = 6:32=20 AM
To:=20 PSN-L@..............
Subject:=20 Emon7.2

 

Does anyone have a copy = of Emon=20 7.2 with support for the Axiom AX-5210 A/D board that they could send = me=20 please.

Thanks,

Alby,

Martin Observatory, = Western=20 = Australia.

Subject: RE: Emon7.2 From: "Bob Shannon" earth@........... Date: Sat, 3 Jul 2004 14:45:02 -0700 Danke Mucho! It was originally a fine program that developed into a great program. Alan is so humble about his work.and to anyone still using DOS.(r there such people?). it is pretty darn nice for an older machine. -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Steve Hammond Sent: Saturday, July 03, 2004 11:58 AM To: psn-l@.............. Subject: RE: Emon7.2 Hi Bob, in a side note I have sent you the Seismic II zip you requested. My version is from 1993... I tested it and it still works. Regards, Steve Hammond PSN San Jose, Aptos CA

Danke Mucho! It was originally a fine program that developed into = a great program. Alan is so humble about his work…and to anyone = still using DOS…(r there such people?)… it is = pretty darn nice for an older machine.

 

 

-----Original = Message-----
From: = psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of Steve Hammond
Sent: = Saturday, July 03, = 2004 11:58 AM
To: = psn-l@..............
Subject: RE: = Emon7.2

 

Hi Bob, in a = side note I have sent you the Seismic II zip you requested. My version is from = 1993... I tested it and it still works.

Regards, Steve = Hammond

PSN = San Jose, Aptos CA<= /st1:State>

 

Subject: Network event reports From: Arie Verveer greensky@............ Date: Wed, 07 Jul 2004 20:43:05 +0800 Hi, It's been a while since I used the "Network Event Reports" function in Winquake, and it appears my old, "recent worldwide quake" (finger) address appears to be changed. Anyone, got a working address to current worldwide quakes ? Path: Winquake -> event report -> network Report. Cheers Arie __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Network event reports From: John or Jan Lahr johnjan@........ Date: Wed, 07 Jul 2004 10:27:25 -0600 Hi Arie, Finger is dying or dead due to recently enhanced security provisions made at the USGS. One alternative is: ftp://ghtftp.cr.usgs.gov/pub/cnss/quake Another, with a listing of events for the past two weeks is: ftp://ghtftp.cr.usgs.gov/pub/cnss/cnss_14.fing Hope this helps! John At 06:43 AM 7/7/2004, you wrote: >Hi, It's been a while since I used the "Network Event Reports" function in >Winquake, >and it appears my old, "recent worldwide quake" (finger) address appears >to be >changed. Anyone, got a working address to current worldwide quakes ? >Path: Winquake -> event report -> network Report. > >Cheers > >Arie > > > >__________________________________________________________ > >Public Seismic Network Mailing List (PSN-L) > >To leave this list email PSN-L-REQUEST@.............. with the body of the >message (first line only): unsubscribe >See http://www.seismicnet.com/maillist.html for more information. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Network event reports From: "Larry Cochrane" lcochrane@.............. Date: Wed, 7 Jul 2004 23:44:05 -0700 Hi Arie, If you add the following (without the quotes) to the network.dat file you should get a list similar to the old finger report. "ftp://ghtftp.cr.usgs.gov/pub/cnss/cnss_14.fing (All NEIC Events)" This file is located in the WinQuake root directory. Regards, Larry Cochrane Redwood City, PSN ----- Original Message ----- From: "Arie Verveer" To: < " > Sent: Wednesday, July 07, 2004 5:43 AM Subject: Network event reports > Hi, It's been a while since I used the "Network Event Reports" function > in Winquake, > and it appears my old, "recent worldwide quake" (finger) address > appears to be > changed. Anyone, got a working address to current worldwide quakes ? > > Path: Winquake -> event report -> network Report. > > Cheers > > Arie > > > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: What is your advice? From: "rem11560@............ rem11560@netzero.com Date: Sun, 11 Jul 2004 16:53:26 GMT Hi Larry, I know that I am a fuss pot, but I would like to submit the following advice to the PSN List. I need your input before I do. I practice what I preach, and I think the files that I now regularly submit are as good or better than most that I see. I am especially annoyed that hardly anyone takes the trouble to calibrate their sensors. Maybe there should be a discussion among list members and a concensus reached on what advice to amateurs would be best to prominently and permanently post on your web site. I also don't like overly large over-sampled files. I would think that you would rather not have to archive such files. Regards, Bob McClure Locust Valley, NY >Re: What is your advice? >Hi Bob, >I don't have a problem with you sending out your request to the PSN list. >-Larry ~~~~~~~~~~~~~ HELPFUL HINTS FROM A FUSSY ELDERLY SEISMIC DATA LOGGER: 1. Be sure that your STATION COORDINATES are correct. You can use Microsoft Streets and Trips, or online MapQuest for the purpose. Also align horizontal sensors to true North or East, or else give true direction in sensor comments box. 2. LOCK your timing to GPS or WWV or a crystal clock slaved to WWVB. 3. CALIBRATE YOUR SENSOR. You would not have much use for a voltmeter with no scale on it, would you?. For open loop sensors, I have two methods. One uses the raw sensor output of pendulum movement between fixed stops, the other measures the force exerted by the pendulum in response to a known current. I can tell you more if you ask. 4. DO NOT submit files with high sample rates on distant teleseisms. High frequencies are attenuated with distance, and files with excessive sample rate only take up bandwidth and archival storage space. Decimate before submitting. One to five samples per second should handle most teleseisms without loss of waveform detail. Also, do not cover an overly large time span after the L wave onset. 5. DO NOT use any more FILTERING than absolutely necessary. Let some microseisms come through. Leave it to the downloader of files do more filtering if they wish. 6. If possible, adjust your sensor's NATURAL PERIOD to least 16 seconds if you record and report teleseisms. If that is not practical, I have written an application program for WinQuake files which can digitally extend the effective period of your sensor by up to a factor of five. I use it routinely on my sensors which have natural periods of 5, 8, and 14 seconds to extend their response to 24 seconds. 7. Control your sensor DAMPING. The barest amount of overshoot on a displaced pendulum is about right. 8. Use as little AMPLIFIER GAIN as possible to avoid clipping on major events. Most of the files I see on the seismicnet site have been recorded at far more gain than necessary. You may have to make component value changes in your amplifier to accomplish this. ~~~~~~~~~~~~~~~ ________________________________________________________________ The best thing to hit the Internet in years - NetZero HiSpeed! Surf the Web up to FIVE TIMES FASTER! Only $14.95/ month -visit www.netzero.com to sign up today! __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: What is your advice? From: "Steve Hammond" shammon1@............. Date: Sun, 11 Jul 2004 11:16:01 -0700 Boy, this could become an ugly discussion. I'm sure there is a few people that don't agree with your comments and parts of them will be taken very personally. For example, if you are talking about the AT1 and AT2 sensors in Aptos, I will be the first to tell you that they are crap and I'm very unhappy with their operation. I was forced to cut the booms down in size because I didn’t have the physical space needed for 38-in. booms, which is what I had used in the San Jose location. Additionally, I only have one spot in my small yard for the seismic box and the cover box will only align off the N/S axis, which limits the boom direction to be off the N/S axis. Let me put it this way, getting the existing hardware to a period of greater than 12-14 seconds will require divine intervention. My point is this; I don’t care if the person submitting the data provides it from a magnet daggling from a string, if they wish to contribute to the dataset, they can. This is the “Public Seismic Network” and all are welcome to take part, regardless of how crappy their equipment is. Instead of stating hard fast rules, I think we should describe desired results as goals. I would like to discuses the goal of sample rates. I believe the teleseimic sample rate goal should be 25 SPS. While Ed Cranswick of the USGS is not here to defend himself, I base this goal on a discussion I had with him in 1991. Ed said, and this is not an exact quote, “any data sampled below 25 samples per second is worthless for future study. Most researchers prefer to extrapolate the needed research data themselves. They would also prefer the data be unfiltered so that they can apply the needed filters. Data that has been highly processed is suspect because the processing algorithms are unknown and not documented and therefore the data may not represent the actual event.” Regards, Steve Hammond PSN San Jose -- Aptos, CA -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@................. Behalf Of rem11560@........... Sent: Sunday, July 11, 2004 9:53 AM To: psn-l@.............. Subject: What is your advice? Hi Larry, I know that I am a fuss pot, but I would like to submit the following advice to the PSN List. I need your input before I do. I practice what I preach, and I think the files that I now regularly submit are as good or better than most that I see. I am especially annoyed that hardly anyone takes the trouble to calibrate their sensors. Maybe there should be a discussion among list members and a concensus reached on what advice to amateurs would be best to prominently and permanently post on your web site. I also don't like overly large over-sampled files. I would think that you would rather not have to archive such files. Regards, Bob McClure Locust Valley, NY >Re: What is your advice? >Hi Bob, >I don't have a problem with you sending out your request to the PSN list. >-Larry ~~~~~~~~~~~~~ HELPFUL HINTS FROM A FUSSY ELDERLY SEISMIC DATA LOGGER: 1. Be sure that your STATION COORDINATES are correct. You can use Microsoft Streets and Trips, or online MapQuest for the purpose. Also align horizontal sensors to true North or East, or else give true direction in sensor comments box. 2. LOCK your timing to GPS or WWV or a crystal clock slaved to WWVB. 3. CALIBRATE YOUR SENSOR. You would not have much use for a voltmeter with no scale on it, would you?. For open loop sensors, I have two methods. One uses the raw sensor output of pendulum movement between fixed stops, the other measures the force exerted by the pendulum in response to a known current. I can tell you more if you ask. 4. DO NOT submit files with high sample rates on distant teleseisms. High frequencies are attenuated with distance, and files with excessive sample rate only take up bandwidth and archival storage space. Decimate before submitting. One to five samples per second should handle most teleseisms without loss of waveform detail. Also, do not cover an overly large time span after the L wave onset. 5. DO NOT use any more FILTERING than absolutely necessary. Let some microseisms come through. Leave it to the downloader of files do more filtering if they wish. 6. If possible, adjust your sensor's NATURAL PERIOD to least 16 seconds if you record and report teleseisms. If that is not practical, I have written an application program for WinQuake files which can digitally extend the effective period of your sensor by up to a factor of five. I use it routinely on my sensors which have natural periods of 5, 8, and 14 seconds to extend their response to 24 seconds. 7. Control your sensor DAMPING. The barest amount of overshoot on a displaced pendulum is about right. 8. Use as little AMPLIFIER GAIN as possible to avoid clipping on major events. Most of the files I see on the seismicnet site have been recorded at far more gain than necessary. You may have to make component value changes in your amplifier to accomplish this. ~~~~~~~~~~~~~~~ ________________________________________________________________ The best thing to hit the Internet in years - NetZero HiSpeed! Surf the Web up to FIVE TIMES FASTER! Only $14.95/ month -visit www.netzero.com to sign up today! __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: "What is your advice?" From: Douglas Gavilanes gavilan1@............. Date: Mon, 12 Jul 2004 12:29:39 -0700 psn-l-digest-request@.............. wrote: > *SNIP* > >Instead of stating hard fast rules, I think we should describe desired >results as goals. I would like to discuses the goal of sample rates. I >believe the teleseimic sample rate goal should be 25 SPS. While Ed Cranswick >of the USGS is not here to defend himself, I base this goal on a discussion >I had with him in 1991. Ed said, and this is not an exact quote, “any data >sampled below 25 samples per second is worthless for future study. Most >researchers prefer to extrapolate the needed research data themselves. They >would also prefer the data be unfiltered so that they can apply the needed >filters. Data that has been highly processed is suspect because the >processing algorithms are unknown and not documented and therefore the data >may not represent the actual event.” > >Regards, Steve Hammond PSN San Jose -- Aptos, CA > > What he said. ;-) Best Regards, Doug Gavilanes Garden Grove, CA. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: What is your advice? From: Jason Brady jr_brady@........... Date: Mon, 12 Jul 2004 13:22:31 -0700 All, I appreciate Bob's suggestions. Straightforward, succinct guidelines like this are invaluable for newcomers like me. If I understand correctly, he is striving for quality and uniformity of data. Ensuring that an instrument is calibrated and processing parameters correctly set/optimized is crucial to achieving that goal. On the other hand, it appears that amateur instruments and processing environments are unique--so how does one define and enforce a set of reasonable standards for data submission? I'm too new to even guess at this point. But perhaps Bob is on the right track with his suggestions. Regarding event data, what would really be helpful is a guidebook with examples to assist new people with understanding how to use their seismo equipment. Examples: how to recognize actual events vs. background noise and understand the intricacies of recording seismic events. Math and engineering aren't my strong suits (I've got precious few of them anyway) and need all the help I can get. Perhaps something like this already exists? Just my $.02. Thanks, Jason Brady __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: What is your advice? From: "Steve Hammond" shammon1@............. Date: Mon, 12 Jul 2004 15:45:49 -0700 Hi Jason (and others'), please don't misunderstand my comments. I'm a college professor and tend to make my concerns heard. This time I happened to make my comment heard during the middle off grading mid-terms when I took a little time to do my Email... I think the PSN should have guidelines for data. I just don't think they should be any specific requirements to submit data to Larry's site other than what Larry requires. Larry has rejected a few of my datasets recently when converting to his new serial data collection system using WinSDR because of data integrity issues. I didn't have the correct information in some of the required fields. I think that Larry acted correctly in doing so. My concern with the original suggestion was that we are an open group and all that wish to contribute should be allowed to do so. I think that every point that was made in the original note is a valid point and we should have a guideline for each point made. But, it should be in the form of goals and not rules / requirements for the data. This is armature seismology group and my first seismograph was built from a 3/8 brass rod with water filled toilet tank float for mass weight. The guys' from the USGS would ask me to keep the cover closed when there was a photographer around. However, that did not stop me from taking part or them from evaluating and reviewing my data. I think we should continue with the same tradition. I suggest we start working on the "Data Collection Goals" and that they be described in a FRQ. What do you think the SPS goal for a distant seismic event should be? I'm current running my AT1 and AT2 devices at 25 SPS based on Ed Cranswick suggestion. Do you feel this is too high or to low? Why? On item 3. CALIBRATE YOUR SENSOR, Bob, this sounds like you have put a lot of work into this. Could you send me the write-ups or are they posted some place? I would be happy to try your methods. I'm already certain the damping magnets on my LP's are not strong enough. I have them right up agents the brass bar and the WAWA test looks OK on one but the other is questionable. I have been using events to fine tune the settings in WinSDR for sensor correction values. A few event-mag values have been correct and a few have not. I'm about 50/50 right now. Regards, Steve Hammond PSN San Jose Aptos, CA -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@................. Behalf Of Jason Brady Sent: Monday, July 12, 2004 1:23 PM To: PSN-L@.............. Subject: What is your advice? All, I appreciate Bob's suggestions. Straightforward, succinct guidelines like this are invaluable for newcomers like me. If I understand correctly, he is striving for quality and uniformity of data. Ensuring that an instrument is calibrated and processing parameters correctly set/optimized is crucial to achieving that goal. On the other hand, it appears that amateur instruments and processing environments are unique--so how does one define and enforce a set of reasonable standards for data submission? I'm too new to even guess at this point. But perhaps Bob is on the right track with his suggestions. Regarding event data, what would really be helpful is a guidebook with examples to assist new people with understanding how to use their seismo equipment. Examples: how to recognize actual events vs. background noise and understand the intricacies of recording seismic events. Math and engineering aren't my strong suits (I've got precious few of them anyway) and need all the help I can get. Perhaps something like this already exists? Just my $.02. Thanks, Jason Brady __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: feasible maximum mass for a Lehman seismometer From: "tdick" dickthomas01@............. Date: Mon, 12 Jul 2004 20:09:38 -0500 At the risk of ruining a good discussion going on the last couple of = days -- I would like to have some input on what the best/maximum mass = for Lehman horizontal seismometer
At the risk of ruining a good = discussion going on=20 the last couple of days -- I would like to have some input on what the=20 best/maximum  mass for Lehman horizontal=20 seismometer
Subject: Dup messages From: "Kareem" kareem@............. Date: Mon, 12 Jul 2004 18:28:39 -0700 Hi PSN, Just to let you know... I've been receiving duplicate messages from the PSN list serv. Not sure why.. Is it me? Kareem __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: seismometer calibration From: BOB BARNS royb1@........... Date: Mon, 12 Jul 2004 21:37:46 -0400 Hi gang, There has been some recent discussion about calibrating seismometers. Several years ago, my article on a calibrator using a meter movement as a force transducer was put on our 'home' www.seismic.com. Go to "Build Your Own Seismographic Station" then to "Article by Bob Barns". Jack Ivey built one these and I asked him to describe his experience. His reply is below. It includes an interesting remark about differences in behavior between large and small motions. I have not seen this discussed before. We would benefit if others with experience with the calibrator were to report. Bob Barns =========== Bob, I used the calibrator extensively in determining the response of a couple of my Lehman derivatives. I found it very easy to set up and use and indispensable in determining the period and damping of the system, even if you aren't terribly interested in the absolute calibration of your seismometer. This is because the return force and damping of a practical Lehman system can be quite nonlinear, and if you adjust the period and damping by bumping the boom with your thumb and eyeballing it, the behavior is quite different than when you start measuring nanometer-scale movements (I found there was way less damping for small displacements than for large). The calibrator is one of the only practical ways I've seen to apply the tiny force needed. I also think the quakes people post would be considerably more interesting if they had an engineering units scale marked. I tried to use your arrangement to calibrate my force-feedback add-on to a 1-second vertical, however the force produced by the meter movement was too small to be useful. It would be nice to have an arrangement that produces 10x or 100x the force for that application (I sacrificed several types of meter in the attempt). You're welcome to use these comments as you wish, no need to credit me. Jack ============================== -----Original Message----- __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: feasible maximum mass for a Lehman seismometer From: "Connie and Jim Lehman" lehmancj@........... Date: Tue, 13 Jul 2004 10:12:39 -0400 T.Dick--thanks for your inquiry. I can only comment on the original = design and how we arrived at the mass. The first model had a boom of = 140 cm and a mass of 4kg or about 9 lbs.--empirical all the way. Those = early Jesuit "cantilever" systems used much heavier masses, as they were = friction linked to give a mechanical readout on smoked paper, but later = , a reflected beam of light on photographic paper reduced the need for = such a heavy mass. The mass is related to the natural period of swing somewhat--(even = though different masses of a bob on a free hanging pendulum makes little = difference in period). More important--the mass must be = supported...The support wire at the angle with horizontal suggested must = be strong. If you do the arithmetic, a 5 lb mass will tug a tension of = between 30 & 40 lbs on the upright hinge area when the angle is 30-40 = degrees. ((Now if you want a real puzzle. As that angle goes to zero, = the tension approaches infinity)) When we made the final design as published, a 5 lb mass was suggested = as 5 lb "bricks" of lead were available. We reduced the boom to fit = everything under a 1 meter box. The physical sensor worked so well with = set up procedure, stability and performance we haven't deviated from = those parameters. That is not saying other parameters won't work. With = care no doubt the physical size of the "Lehman" could be halved, but = instabilites no doubt would frustrate the user. On a bit of related technology. Several years ago we built a = portable Foucault pendulum on a 4-ft tripod, drove it magnetically from = below, and achieved 5% accuracy. We thought this was pretty neat, until = a gentleman from Michigan built a good working model about 12 inches = high. One never quite knows where the empirical approach in mechanical = devices take one!! Best Wishes--Jim Lehman ----- Original Message -----=20 From: tdick=20 To: psn-l@................. Sent: Monday, July 12, 2004 9:09 PM Subject: feasible maximum mass for a Lehman seismometer At the risk of ruining a good discussion going on the last couple of = days -- I would like to have some input on what the best/maximum mass = for Lehman horizontal seismometer
T.Dick--thanks for your inquiry.  = I can only=20 comment on the original design and how we arrived at the mass.  The = first=20 model had a boom of 140 cm and a mass of 4kg or about 9 lbs.--empirical = all the=20 way.  Those early Jesuit "cantilever" systems used much heavier = masses, as=20 they were friction linked to give a mechanical readout on smoked paper, = but=20 later , a reflected beam of light on photographic paper reduced the need = for=20 such a heavy mass.
    The mass is related = to the=20 natural period of swing somewhat--(even though different masses of a bob = on a=20 free hanging pendulum makes little  difference in period).  = More=20 important--the mass must be supported...The support wire at the angle = with=20 horizontal suggested must be strong.  If you do the arithmetic, a 5 = lb mass=20 will tug a tension of between 30 & 40 lbs  on the upright hinge = area=20 when the angle is 30-40 degrees.  ((Now if you want a real = puzzle.  As=20 that angle goes to zero, the tension approaches infinity))
   When we made the final = design as=20 published, a 5 lb mass was suggested as 5 lb "bricks" of lead were=20 available.  We reduced the boom to fit everything under a 1 meter=20 box.  The physical sensor worked so well with set up procedure, = stability=20 and performance we haven't deviated from those parameters.  That is = not=20 saying other parameters won't work.  With care no doubt the = physical size=20 of the "Lehman" could be halved, but instabilites no doubt would = frustrate the=20 user.
    On a bit of related=20 technology.  Several years ago we built a portable Foucault = pendulum on a=20 4-ft tripod, drove it magnetically from below, and achieved 5%=20 accuracy.  We thought this was pretty neat, until a gentleman from = Michigan=20 built a good working model  about 12 inches high.
   One never quite knows = where the=20 empirical approach in mechanical devices take one!!  Best = Wishes--Jim=20 Lehman
----- Original Message -----
From:=20 tdick
Sent: Monday, July 12, 2004 = 9:09 PM
Subject: feasible maximum mass = for a=20 Lehman seismometer

At the risk of ruining a good = discussion going on=20 the last couple of days -- I would like to have some input on what the = best/maximum  mass for Lehman horizontal=20 seismometer
Subject: Sensor calibration From: "rem11560@............ rem11560@netzero.com Date: Tue, 13 Jul 2004 19:33:44 GMT Hi all, Sensor calibration seems to be the topic du jour. Calibration is a tedious but recommended procedure for the serious amateur. I wrote the following note on my calibration method to the PSN List on 07/19/2003, a year ago. At this time, I am adding a dissertation on how to use current applied to the sensor coil and measurement of the resulting force exerted by the coil to achieve calibration. Be reminded of the fact that these calibration methods only determine the sentivity of the sensor for frequencies greater than the natural resonant frequency of the sensor. Sensor response falls very rapidly at frequencies less than the natural frequency. Bob McClure Locust Valley, NY Web page: http://www.jclahr.com/science/psn/mcclure/ ----------------------- APPLIED MOTION METHOD: ----------------------- 1. Set up limit stops on the pendulum so that it can be displaced over a known and fixed number of millimeters at its radius of gyration. 2. Connect the sensor directly to the A/D, and log data as you move the pendulum gently back-and forth a few times between the stops. Record at a rate that gives a reasonable number of samples for the time taken to move between stops. Do not move so fast that you exceed the voltage range of the A/D, otherwise you won't get valid data, and you might even blow out the A/D. Also, verify that the resistance of the sensor coil is low compared to the input impedance of the A/D. 3. Make a WinQuake event file out of the data. 4. Use WinQuake to integrate the data. You should see the actual displacement versus time, measured in counts. Measure the peak-to-peak displacement in counts, using the mouse readout when it is positioned on successive peaks. 5. Scale the count measurement to what you would have obtained for one centimeter of motion. If you used 5mm of displacement, for example, you would multiply your count estimate by two. 6. Multiply the scaled counts by the voltage gain setting of the amplifier you normally use. 7. Take the inverse of the number obtained in step 6. This is the number you should enter for "Sensitivity:" in the Sensor Information Dialog box. ------------ ------------------------ APPLIED CURRENT METHOD: ------------------------ Recall the following from your physics textbook: Generator Law: Volts= B*L*(dx/dt), where B= magnetic field in Teslas, L= total length of wire in meters cutting flux lines, (dx/dt)= velocity of coil motion in meters per second. Motor Law: Force=B*L*I where F= force in newtons, B in Teslas, L in meters. Combining the two laws, we obtain V/(dx/dt) = F/I so, if we measure F/I we know V/(dx/dt), the sensor output in volt-seconds per meter. We don't need to know anything about magnetic field strength or coil configuration. One newton is the force required to accelerate one kilogram mass at one meter per second. In grams, it is 1000/9.8 = 102.04. Suppose we apply a current of 5 milliamperes to the coil and measure a force of 40 grams. I=.005 amperes, F= 40/102.04= .392, F/I= 78.4 volt-seconds per meter. ~~~~~~~~~~~~~ The equation is simple, but execution of the measurement is not. If you use a countertop digital scale, you have to figure out how to transmit the force from the sensor to the scale. This ususually would require rigging up levers and pushrods. I did this measurement, but using only the component parts -- the magnet and the coil. My coil is a flat pancake, positioned in a 4-pole Nd magnet assembly. What I did was to place the magnet on edge on the scale, and make up a rig to hold the coil in place from the counter top. I then measured the apparent change in the weight of the magnet as current was applied in either direction to the coil. If you use a heavy magnet, you will probably have to secure the coil to the scale, and the magnet to the counter top. Estimate coil current by dividing the applied DC voltage by the coil resistance in ohms. If you have a sensitive spring scale, that's great. You can probably use it on an assembled sensor. Just be sure that you pull the boom back to its normal rest position when the scale is being pulled upon by the current being applied to the coil. Measure how far from the boom pivot you took the force reading, and estimate the radius of gyration of the pendulum. By whatever means you measure force, you will have to figure out what the force actually would be at the radiu of gyration, which is not usually at the center of the coil. You will have to make lever arm corrections to convert the measured force at the point of measurement to the force at the radius of gyration, which in most cases is very near the center of the extra mass added to the boom. After you have made the F/I measurement, make the lever arm correction to find the equivalent value at the center of gyration. Divide this F/I by 100 to get volt-seconds per centimeter, and multiply that result by your amplifier's voltage gain. Next, divide your A/D's full scale volts by the full scale digital word value. Usually, you will be dividing 10 by 32,768, yielding 0.000305176 volts per bit. Divide the result by the amplified F/I to get the number to be entered for sensitivity in WinQuake. You also have the option of letting WinQuake do the calculations for you. Just enter the sensor output (volt-seconds per centimeter) in the "Output Voltage:" box, the amplifier voltage gain in the "Amp Gain:" box, the A/D full scale voltage in the "A/D Voltage:" box, and the A/D bit number in the "A/D Bits:" box, and then click on the "Calc Sens" box. (Note to Dataq users: Always enter 16 for A/D bits, even though the actual number is less. Dataq always scales 10 volts to digital value 32,768, regardless of the number of active bits in the device.) ~~~~~~~~~~~~~~~~~~~~~~ Afterthoughts: If you use shunt resistance across the coil to provide damping, you may have to reduce your measured sensor output calibration value. The reduction factor is (Rshunt/(Rshunt + Rcoil). The value of Rshunt must also include the contribution of the amplifier input impedance: 1/Rshunt = 1/Rexternal + 1/Ramplifier. I recommend the use of shunt damping whenever possible because it permits easy measurement of natural period (with the shunt removed) and precise control of the degree of damping (amount of shunt conductance applied). It is easiest to use if your sensor has high output combined with low pendulum mass and low coil resistance. The conventional massive Lehman design may not have such properties, however. My own horizontal sensors are at the other extreme. They have a coil resistance of only 340 ohms, a pendulum mass of around 70 grams, and an output of 0.8 volt-sec/cm. Critical damping requires only 30K of shunt resistance. My amplifier input impedance is 100K, and so I add another 90K across that to get proper damping. My vertical sensor is more like a Lehman, with much more mass and much more coil resistance. Even so, I use shunt damping on it, at the loss of some sensitivity. If you are building a sensor, consider the use of multiple magnets. If you place a horseshoe magnet on one side of the coil, place another with poles reversed on the opposite side. You will get twice the output, and much better linearity. My own preference is a 4-pole magnet assembly using powerful Nd block magnets, a narrow gap, and a pancake coil. ________________________________________________________________ The best thing to hit the Internet in years - NetZero HiSpeed! Surf the Web up to FIVE TIMES FASTER! Only $14.95/ month -visit www.netzero.com to sign up today! __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: feasible maximum mass for a Lehman seismometer From: "tdick" dickthomas01@............. Date: Tue, 13 Jul 2004 16:27:43 -0500 I have two running now and am preparing to make changes. I used = speaker magnets plus a five lb piece of lead on the boom which is over = 30 inches long and 5/8 thick. I am thinking of imbedding a ball bearing = in the end of the shaft, adding another 5 lbs of lead and putting the = coil of wire on the boom instead of on the base, making the magnet = stationary.
 
I have two = running now=20 and am preparing to make changes. I used speaker magnets plus a five = lb piece=20 of lead on the boom which is over 30 inches long and 5/8 thick. I am = thinking=20 of imbedding a ball bearing in the end of the shaft, adding another 5 = lbs of=20 lead and putting the coil of wire on the boom instead of on the base, = making=20 the magnet stationary.
Subject: infrasounds From: "jse" jse@............ Date: Sat, 17 Jul 2004 12:12:32 +0430 Hi all, I am thinking to build a easy seismometre. Is possible to detect infrasouns in the atmosphera with this seismometre? which seismometre would be the adequate for this objective? Best Regards =20
Hi all,
 
I am thinking to build a easy = seismometre.
Is=20 possible to  detect infrasouns in the atmosphera
with this=20 seismometre?
which seismometre would be the adequate for this=20 objective?
 
Best Regards

 
Subject: Re: infrasounds From: Arie Verveer greensky@............ Date: Sun, 18 Jul 2004 11:17:44 +0800 Well sort off. I have detected Infra-sound from major fireball reentry's but these are major regional events. The infra-sound impinges on the ground and your seismograph detects the vibration. This vibration is in the upper portion of the seismic spectra , say 0.5 hertz and above. By the way, sound is refracted in the atmosphere just like seismic waves are refracted in the earth. Also, infra-sound will refract up in the atmosphere and eventually refract back to to the earth then reflect off the earth surface, and so on. The wave pattern becomes very complex very quickly. So any possible detection within a few hundred kilometers will soon just look like the seismic background. Infra-sound from meteors can radiate down and cause the infra-sound to seismic signature. To detect infrasound you really need a specific detector. Actually, I just have started the third generation of this type of detector. When It's working I'll drop an email to this site with construction details. Arie jse wrote: > Hi all, > > I am thinking to build a easy seismometre. > Is possible to detect infrasouns in the atmosphera > with this seismometre? > which seismometre would be the adequate for this objective? > > Best Regards > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: FW: Re: what is your advice? From: "Meredith Lamb" meredithlamb@............. Date: Tue, 20 Jul 2004 23:16:13 -0600 The following msg is being forwarded and was reply written by Chris Chapman: Hi All, A few more comments on seismometers.... HELPFUL HINTS FROM A FUSSY ELDERLY SEISMIC DATA LOGGER: 1. Be sure that your STATION CO-ORDINATES are correct. You can use Microsoft Streets and Trips, or online MapQuest for the purpose. Also align horizontal sensors to true North or East, or else give true direction in sensor comments box. OK on the alignment and reporting. Full details would often be most helpful. As far as I can see, the Lat/Long search option has now been removed from Mapquest. The Microsoft Streets and Trips CD only gives information for the USA and parts of Canada. Has anyone got a reference for a world wide map programme which you can use with Lat + Long? 2. LOCK your timing to GPS or WWV or a crystal clock slaved to WWVB. Fine, but it would be helpful if Larry included a programme which DECODED the WWVB minute long signals directly and could also update the clock at user defined intervals. WWVB modules are available. The receive limit is set by local radio interference / noise, but can be expected to be >2,000 miles at night. Keep the receiver well away (10 ft +) from a CRT display. The effective signal coverage is shown at http://www.boulder.nist.gov/timefreq/stations/wwvbcoverage.htm 3. CALIBRATE YOUR SENSOR. You would not have much use for a voltmeter with no scale on it, would you? For open loop sensors, I have two methods. One uses the raw sensor output of pendulum movement between fixed stops, the other measures the force exerted by the pendulum in response to a known current. I can tell you more if you ask. Remembering that seismometers are used which measure displacement, or velocity or acceleration, so we need several calibration methods. Remember also that the signal which you actually see can depend quite strongly on the local sub surface geological structures. If you are sitting on a thick layer of water saturated alluvial soil, it can shake much like a jelly. If your seismometer is calibrated in say volts / metre / sec, you may see some variation in signal with the reception angle and there may be large errors in the calculated amplitude / distance measurement. An alternative method is to measure the recorded amplitude of a series of 'known' quakes and then make up a rough correlation table. 4. DO NOT submit files with high sample rates on distant teleseisms. High frequencies are attenuated with distance, and files with excessive sample rate only take up bandwidth and archival storage space. Decimate before submitting. One to five samples per second should handle most teleseisms without loss of waveform detail. Also, do not cover an overly large time span after the L wave onset. You will have difficulty in separating out the P and S waves if your system cannot reproduce 0.5 to 1 Hz quite accurately. I would suggest that 10 sps is a more reasonable compromise. Local quakes also have P & S components of higher frequency. Some locations have relatively high damping down to below about 1/2 Hz. If you also have high environmental noise, you may have difficulty in resolving quake arrival times. 5. DO NOT use any more FILTERING than absolutely necessary. Let some microseisms come through. Leave it to the downloader of files do more filtering if they wish. Sure, but it is helpful if you can at least recognise the outline of the earthquake signal. I don't find a seismic signal which completely masked in either high frequency environmental or in instrument noise, very helpful. 6. If possible, adjust your sensor's NATURAL PERIOD to least 16 seconds if you record and report teleseisms. If that is not practical, I have written an application program for WinQuake files which can digitally extend the effective period of your sensor by up to a factor of five. I use it routinely on my sensors which have natural periods of 5, 8, and 14 seconds to extend their response to 24 seconds. This does depend on what sort of seismometer you use and on it's natural period. Local environmental noise may become serious by 10 Hz. The Ocean background will give quite large signals somewhere between 2 and 10 seconds, which need to be filtered out. Twin Tee rejection filters have been used successfully and can give over 50 dB peak rejection. The frequency and the amplitude may change with time. Using beam type seismometers, it is desirable to have the period between 20 and 30 seconds. A 10 second to 30 second range allows good detection of L & R waves. Simple damped pendulum seismometers with a 1.4 sec period are popular in Europe and pickup P & S waves quite nicely. 7. Control your sensor DAMPING. The barest amount of overshoot on a displaced pendulum is about right. I agree, but this is the ONE FACTOR in seismometer construction which is likely to give MOST PROBLEMS. I found it DIFFICULT to set up an oil damped system to about 0.8 x critical. I found it NEAR IMPOSSIBLE to keep it that way without oil temperature control, or frequent measurement / re-setup. Oil is messy, attracts dust, creeps over all surfaces, drowns insects (which then give 'bug quakes') and the viscosity is strongly temperature dependant. The surface tension also varies, which can give beam drift. For oil systems, you need to measure the damping for very small displacements - use your SDR recording programme to monitor and display this. If you pull the mass 1/2" to one side and then release it, you may observe a significantly higher damping due to swirl in the oil and the system may still be under-damped for normal seismic signals. I honestly don't know why anyone would try to use oil damping these days. EM damping using NdFeB magnets is simple, cheap, clean, easy to set up and to adjust. For a Lehman, the damping required is also strongly dependant on the period you choose and hence on the suspension adjustment. You need a fair range of damping adjustment available. There are two ways of providing electromagnetic damping. You can either use a flat Al or Cu plate in a pole gap with a strong magnetic field, or you can use a coil of wire half in the field and put a loading resistor across it. After having set up the period, you choose a load resistor (by experiment) which gives near critical damping. This was done with the cylindrical coils and magnets in the Sprengnether seismometers. However, the sensitivity then depends on the value of the damping resistor, which complicates matters. I prefer to keep the damping and sensor coil functions separate. With two N+S pairs of opposing flat magnets 1" x 1/2" x 1/4" on 1/4" baseplates, you just move the high central field over a 1/16" to 1/8" thick Al or copper tongue till you get the desired damping. Electro magnetic damping is far easier to adjust than oil damping and with the ready availability of strong NdFeB magnets, it is cheap and simple to implement. Suppliers are Sedona2 on Ebay, Amazing Magnets (occasional E-Bay), "Emovendo" on ebay only (perhaps the cheapest N48 supplier), K&J magnetics ( wide range) www.kjmagnetics.com and www.wondermagnet.com 8. Use as little AMPLIFIER GAIN as possible to avoid clipping on major events. Most of the files I see on the seismicnet site have been recorded at far more gain than necessary. You may have to make component value changes in your amplifier to accomplish this. Agreed, but the practical choice is likely to depend on the local environmental noise and on the Ocean background. You want to be able to resolve the background signals at times of "low noise", but you don't want strong quakes to saturate the sensor. Most amateurs do not have the option of siting their seismometer in quiet rural area. If you use 'period extending' software, you will need more amplification to cope with the lower amplitude of the longer period waves. You are likely to get uncertain readings if you are amplifying noise. 16 bit A/D converters, with three bits of converter noise, are not too helpful in this respect. Perhaps we could agree on a rough amplitude for the ocean background signals? The gain you can use also depends on the noise and resolution in your A/D Converter. A/D Converter boards with +/-1/2 LSB resolved internal noise are available. >> Subject: feasible maximum mass for a Lehman seismometer At the risk of ruining a good discussion going on the last couple of days -- I would like to have some input on what the best / maximum mass for Lehman horizontal seismometer. The best mass is the lowest which gives you clear low noise signals. This advice 'begs the question'. The 'kt' thermal excitation noise sets the minimum seismic mass at about an ounce, so you are better with 1/2 lb, minimum. If you use a solid metal beam, as opposed to a tube or a U channel, the moment of inertia of the beam can actually reduce the 'radius of gyration k' of the combined beam + seismic mass, giving a shorter period than you would get from the seismic mass at the end of a weightless arm. The beam needs to be light but rigid (aim for a tube weight less end fittings 1/4 the weight of the seismic mass or less). I have found the light 1/2" nominal welded stainless steel water pipe to be very satisfactory. The thermal expansion coefficient matches that of a piano wire suspension quite well. It is also cheap and you can buy brass compression fittings on which to mount the suspension, the seismic mass and the damping components. This makes the construction quite easy. This said, the period of a simple pendulum is independent of the mass. It is advisable to keep the boom length between 70 cm and 100 cm. This is because you are using the garden gate type of suspension and shorter lengths require you to set up the side to side level position with rapidly increasing precision. This can make a 12" beam not only exceptionally difficult to adjust, but very sensitive to tilt drift, either from the suspension system or from natural earth movements. Using a 30/60/90 degree triangle suspension is fine. Try to keep the boom / wire angle above 20 deg, or the suspension loading will be large. You can buy nickel coated 8 thou steel wire from a music shop, for stringing mandolins. To clamp wire, I drill a 1/16" hole just under the head of a bolt. Then I 'dish' a couple of washers by putting them on a wood block and hitting the centre hole with a large centre punch + hammer. You put the two washers on the bolt with the outer cup edges touching and feed the wire between these edges and through the hole in the bolt. This gives a good 'edge clamp' on the wire. For adjustment screws, I use stainless steel nuts and bolts bought from a marine / boat-builder supplier. I drill out the threaded end of the bolt with a centre drill and stick a stainless ball bearing in the conical hole. I drill a plain hole in the baseplate and stick a nut onto the lower side with methacrylate or epoxy cement. It is essential that the bolt and the nut are made of the same material, or the adjustment will drift with change in temperature. I usually use a second nut + a spring washer on the lower side of the mounting nut to provide tensioning / alignment in the thread. I stick stainless steel mounting plates onto the concrete floor, either with the special concrete 'pool adhesive' or with epoxy. If you use epoxy, it is a good idea to dry out the top of the cement thoroughly with a warm air blower. Lastly: >> Hi gang, There has been some recent discussion about calibrating seismometers. Several years ago, my article on a calibrator using a meter movement as a force transducer was put on our 'home' www.seismic.com. Go to "Build Your Own Seismographic Station" then to "Article by Bob Barns". ?? Can anyone help me find this article, please? www seismic.com seems like a huge website with lots of advertising, but only a very old article on seismology. 'Earth Science' seems to be just advertising vitamins... If you want a force calibration system with much higher forces than a meter movement, you can use a small NdFeB cube magnet with a Maxwell coil. These look similar to a Helmholtz coil, but with double the winding spacing and the windings connected in opposition. This gives a constant field gradient. You can calibrate it using a pendulum of a known length and mass, by measuring the deflection / coil current. Regards, Chris Chapman
 
The following msg is being forwarded and was reply written by Chris Chapman:
 
Hi All,
 
    A few more comments on seismometers....
 
HELPFUL HINTS FROM A FUSSY ELDERLY SEISMIC DATA LOGGER:
1. Be sure that your STATION CO-ORDINATES are correct. You can use Microsoft Streets and Trips, or online MapQuest for the purpose. Also align horizontal sensors to true North or East, or else give true direction in sensor comments box.
    OK on the alignment and reporting. Full details would often be most helpful.
 
     As far as I can see, the Lat/Long search option has now been removed from Mapquest. 
 
    The Microsoft Streets and Trips CD only gives information for the USA and parts of Canada.
 
    Has anyone got a reference for a world wide map programme which you can use with Lat + Long?
2. LOCK your timing to GPS or WWV or a crystal clock slaved to WWVB.
    Fine, but it would be helpful if Larry included a programme which DECODED the WWVB minute long signals directly and could also update the clock at user defined intervals. WWVB modules are available. The receive limit is set by local radio interference / noise, but can be expected to be >2,000 miles at night. Keep the receiver well away (10 ft +) from a CRT display. The effective signal coverage is shown at http://www.boulder.nist.gov/timefreq/stations/wwvbcoverage.htm  
3. CALIBRATE YOUR SENSOR. You would not have much use for a voltmeter with no scale on it, would you? For open loop sensors, I have two methods. One uses the raw sensor output of pendulum movement between fixed stops, the other measures the force exerted by the pendulum in response to a known current. I can tell you more if you ask.
    Remembering that seismometers are used which measure displacement, or velocity or acceleration, so we need several calibration methods.
    Remember also that the signal which you actually see can depend quite strongly on the local sub surface geological structures. If you are sitting on a thick layer of water saturated alluvial soil, it can shake much like a jelly. If your seismometer is calibrated in say volts / metre / sec, you may see some variation in signal with the reception angle and there may be large errors in the calculated amplitude / distance measurement. An alternative method is to measure the recorded amplitude of a series of 'known' quakes and then make up a rough correlation table. 
4. DO NOT submit files with high sample rates on distant teleseisms. High frequencies are attenuated with distance, and files with excessive sample rate only take up bandwidth and archival storage space. Decimate before submitting. One to five samples per second should handle most teleseisms without loss of waveform detail. Also, do not cover an overly large time span after the L wave onset.
      You will have difficulty in separating out the P and S waves if your system cannot reproduce 0.5 to 1 Hz quite accurately.
    I would suggest that 10 sps is a more reasonable compromise. Local quakes also have P & S components of higher frequency.
    Some locations have relatively high damping down to below about 1/2 Hz. If you also have high environmental noise, you may have difficulty in resolving quake arrival times.
    
5. DO NOT use any more FILTERING than absolutely necessary. Let some microseisms come through. Leave it to the downloader of files do more filtering if they wish.
    Sure, but it is helpful if you can at least recognise the outline of the earthquake signal. I don't find a seismic signal which completely masked in either high frequency environmental or in instrument noise, very helpful.
6. If possible, adjust your sensor's NATURAL PERIOD to least 16 seconds if you record and report teleseisms. If that is not practical, I have written an application program for WinQuake files which can digitally extend the effective period of your sensor by up to a factor of five. I use it routinely on my sensors which have natural periods of 5, 8, and 14 seconds to extend their response to 24 seconds.
   This does depend on what sort of seismometer you use and on it's natural period. Local environmental noise may become serious by 10 Hz. The Ocean background will give quite large signals somewhere between 2 and 10 seconds, which need to be filtered out. Twin Tee rejection filters have been used successfully and can give over 50 dB peak rejection. The frequency and the amplitude may change with time.
    Using beam type seismometers, it is desirable to have the period between 20 and 30 seconds. A 10 second to 30 second range allows good detection of L & R waves. 
    Simple damped pendulum seismometers with a 1.4 sec period are popular in Europe and pickup P & S waves quite nicely.
7. Control your sensor DAMPING. The barest amount of overshoot on a displaced pendulum is about right.
    I agree, but this is the ONE FACTOR in seismometer construction which is likely to give MOST PROBLEMS. I found it DIFFICULT to set up an oil damped system to about 0.8 x critical. I found it NEAR IMPOSSIBLE to keep it that way without oil temperature control, or frequent measurement / re-setup. Oil is messy, attracts dust, creeps over all surfaces, drowns insects (which then give 'bug quakes') and the viscosity is strongly temperature dependant. The surface tension also varies, which can give beam drift.
    For oil systems, you need to measure the damping for very small displacements - use your SDR recording programme to monitor and display this. If you pull the mass 1/2" to one side and then release it, you may observe a significantly higher damping due to swirl in the oil and the system may still be under-damped for normal seismic signals.
    I honestly don't know why anyone would try to use oil damping these days. EM damping using NdFeB magnets is simple, cheap, clean, easy to set up and to adjust.
    For a Lehman, the damping required is also strongly dependant on the period you choose and hence on the suspension adjustment. You need a fair range of damping adjustment available.
    There are two ways of providing electromagnetic damping. You can either use a flat Al or Cu plate in a pole gap with a strong magnetic field, or you can use a coil of wire half in the field and put a loading resistor across it. After having set up the period, you choose a load resistor (by experiment) which gives near critical damping. This was done with the cylindrical coils and magnets in the Sprengnether seismometers. However, the sensitivity then depends on the value of the damping resistor, which complicates matters.
    I prefer to keep the damping and sensor coil functions separate. With two N+S pairs of opposing flat magnets 1" x 1/2" x 1/4" on 1/4" baseplates, you just move the high central field over a 1/16" to 1/8" thick Al or copper tongue till you get the desired damping.
    Electro magnetic damping is far easier to adjust than oil damping and with the ready availability of strong NdFeB magnets, it is cheap and simple to implement. Suppliers are Sedona2 on Ebay, Amazing Magnets (occasional E-Bay), "Emovendo" on ebay only (perhaps the cheapest N48 supplier), K&J magnetics ( wide range) www.kjmagnetics.com  and www.wondermagnet.com
 
8. Use as little AMPLIFIER GAIN as possible to avoid clipping on major events. Most of the files I see on the seismicnet site have been recorded at far more gain than necessary. You may have to make component value changes in your amplifier to accomplish this.
 
     Agreed, but the practical choice is likely to depend on the local environmental noise and on the Ocean background. You want to be able to resolve the background signals at times of "low noise", but you don't want strong quakes to saturate the sensor. Most amateurs do not have the option of siting their seismometer in quiet rural area.
    If you use 'period extending' software, you will need more amplification to cope with the lower amplitude of the longer period waves. You are likely to get uncertain readings if you are amplifying noise. 16 bit A/D converters, with three bits of converter noise, are not too helpful in this respect.
    Perhaps we could agree on a rough amplitude for the ocean background signals?
    The gain you can use also depends on the noise and resolution in your A/D Converter. A/D Converter boards with +/-1/2 LSB resolved internal noise are available.
 
>>    Subject: feasible maximum mass for a Lehman seismometer
    At the risk of ruining a good discussion going on the last couple of days -- I would like to have some input on what the best / maximum mass for Lehman horizontal seismometer.

     The best mass is the lowest which gives you clear low noise signals. This advice 'begs the question'.
    The 'kt' thermal excitation noise sets the minimum seismic mass at about an ounce, so you are better with 1/2 lb, minimum. 
    If you use a solid metal beam, as opposed to a tube or a U channel, the moment of inertia of the beam can actually reduce the 'radius of gyration k' of the combined beam + seismic mass, giving a shorter period than you would get from the seismic mass at the end of a weightless arm. The beam needs to be light but rigid (aim for a tube weight less end fittings 1/4 the weight of the seismic mass or less). I have found the light 1/2" nominal welded stainless steel water pipe to be very satisfactory. The thermal expansion coefficient matches that of a piano wire suspension quite well. It is also cheap and you can buy brass compression fittings on which to mount the suspension, the seismic mass and the damping components. This makes the construction quite easy.
    This said, the period of a simple pendulum is independent of the mass.
    It is advisable to keep the boom length between 70 cm and 100 cm. This is because you are using the garden gate type of suspension and shorter lengths require you to set up the side to side level position with rapidly increasing precision. This can make a 12" beam not only exceptionally difficult to adjust, but very sensitive to tilt drift, either from the suspension system or from natural earth movements.  
     Using a 30/60/90 degree triangle suspension is fine. Try to keep the boom / wire angle above 20 deg, or the suspension loading will be large. You can buy nickel coated 8 thou steel wire from a music shop, for stringing mandolins. To clamp wire, I drill a 1/16" hole just under the head of a bolt. Then I 'dish' a couple of washers by putting them on a wood block and hitting the centre hole with a large centre punch + hammer. You put the two washers on the bolt with the outer cup edges touching and feed the wire between these edges and through the hole in the bolt. This gives a good 'edge clamp' on the wire.
    For adjustment screws, I use stainless steel nuts and bolts bought from a marine / boat-builder supplier. I drill out the threaded end of the bolt with a centre drill and stick a stainless ball bearing in the conical hole. I drill a plain hole in the baseplate and stick a nut onto the lower side with methacrylate or epoxy cement. It is essential that the bolt and the nut are made of the same material, or the adjustment will drift with change in temperature. I usually use a second nut + a spring washer on the lower side of the mounting nut to provide tensioning / alignment in the thread. I stick stainless steel mounting plates onto the concrete floor, either with the special concrete 'pool adhesive' or with epoxy. If you use epoxy, it is a good idea to dry out the top of the cement thoroughly with a warm air blower.
 
Lastly:
>> Hi gang,
  There has been some recent discussion about calibrating seismometers.    Several years ago, my article on a calibrator using a meter movement as a force transducer was put on our 'home'  www.seismic.com.  Go to "Build Your Own Seismographic Station" then to "Article by Bob Barns".
 
    ?? Can anyone help me find this article, please? www seismic.com seems like a huge website with lots of advertising, but only a very old article on seismology. 'Earth Science' seems to be just advertising vitamins...
 
    If you want a force calibration system with much higher forces than a meter movement, you can use a small NdFeB cube magnet with a Maxwell coil. These look similar to a Helmholtz coil, but with double the winding spacing and the windings connected in opposition. This gives a constant field gradient. You can calibrate it using a pendulum of a known length and mass, by measuring the deflection / coil current.
 
    Regards,
 
    Chris Chapman
Subject: Re: Re: what is your advice? From: "Larry Conklin" lconklin@............ Date: Wed, 21 Jul 2004 11:05:21 -0400 I think we all should petition Chris to write a book on seismometer = construction. I have learned more from reading his postings than just = about any other source. Larry Conklin lconklin@............ ----- Original Message -----=20 From: Meredith Lamb=20 To: psn-l=20 Sent: Wednesday, July 21, 2004 1:16 AM Subject: FW: Re: what is your advice? The following msg is being forwarded and was reply written by Chris = Chapman: Hi All,=20 A few more comments on seismometers.... HELPFUL HINTS FROM A FUSSY ELDERLY SEISMIC DATA LOGGER: 1. Be sure that your STATION CO-ORDINATES are correct. You can use = Microsoft Streets and Trips, or online MapQuest for the purpose. Also = align horizontal sensors to true North or East, or else give true = direction in sensor comments box. OK on the alignment and reporting. Full details would often be = most helpful. As far as I can see, the Lat/Long search option has now been = removed from Mapquest.=20 The Microsoft Streets and Trips CD only gives information for = the USA and parts of Canada.=20 Has anyone got a reference for a world wide map programme which = you can use with Lat + Long? 2. LOCK your timing to GPS or WWV or a crystal clock slaved to = WWVB. Fine, but it would be helpful if Larry included a programme = which DECODED the WWVB minute long signals directly and could also = update the clock at user defined intervals. WWVB modules are available. = The receive limit is set by local radio interference / noise, but can be = expected to be >2,000 miles at night. Keep the receiver well away (10 ft = +) from a CRT display. The effective signal coverage is shown at = http://www.boulder.nist.gov/timefreq/stations/wwvbcoverage.htm =20 3. CALIBRATE YOUR SENSOR. You would not have much use for a = voltmeter with no scale on it, would you? For open loop sensors, I have = two methods. One uses the raw sensor output of pendulum movement between = fixed stops, the other measures the force exerted by the pendulum in = response to a known current. I can tell you more if you ask. Remembering that seismometers are used which measure = displacement, or velocity or acceleration, so we need several = calibration methods.=20 Remember also that the signal which you actually see can depend = quite strongly on the local sub surface geological structures. If you = are sitting on a thick layer of water saturated alluvial soil, it can = shake much like a jelly. If your seismometer is calibrated in say volts = / metre / sec, you may see some variation in signal with the reception = angle and there may be large errors in the calculated amplitude / = distance measurement. An alternative method is to measure the recorded = amplitude of a series of 'known' quakes and then make up a rough = correlation table.=20 4. DO NOT submit files with high sample rates on distant = teleseisms. High frequencies are attenuated with distance, and files = with excessive sample rate only take up bandwidth and archival storage = space. Decimate before submitting. One to five samples per second should = handle most teleseisms without loss of waveform detail. Also, do not = cover an overly large time span after the L wave onset. You will have difficulty in separating out the P and S waves = if your system cannot reproduce 0.5 to 1 Hz quite accurately.=20 I would suggest that 10 sps is a more reasonable compromise. = Local quakes also have P & S components of higher frequency. Some locations have relatively high damping down to below about = 1/2 Hz. If you also have high environmental noise, you may have = difficulty in resolving quake arrival times. =20 5. DO NOT use any more FILTERING than absolutely necessary. Let = some microseisms come through. Leave it to the downloader of files do = more filtering if they wish. Sure, but it is helpful if you can at least recognise the = outline of the earthquake signal. I don't find a seismic signal which = completely masked in either high frequency environmental or in = instrument noise, very helpful. 6. If possible, adjust your sensor's NATURAL PERIOD to least 16 = seconds if you record and report teleseisms. If that is not practical, I = have written an application program for WinQuake files which can = digitally extend the effective period of your sensor by up to a factor = of five. I use it routinely on my sensors which have natural periods of = 5, 8, and 14 seconds to extend their response to 24 seconds. This does depend on what sort of seismometer you use and on it's = natural period. Local environmental noise may become serious by 10 Hz. = The Ocean background will give quite large signals somewhere between 2 = and 10 seconds, which need to be filtered out. Twin Tee rejection = filters have been used successfully and can give over 50 dB peak = rejection. The frequency and the amplitude may change with time. Using beam type seismometers, it is desirable to have the period = between 20 and 30 seconds. A 10 second to 30 second range allows good = detection of L & R waves.=20 Simple damped pendulum seismometers with a 1.4 sec period are = popular in Europe and pickup P & S waves quite nicely. 7. Control your sensor DAMPING. The barest amount of overshoot on = a displaced pendulum is about right. I agree, but this is the ONE FACTOR in seismometer construction = which is likely to give MOST PROBLEMS. I found it DIFFICULT to set up an = oil damped system to about 0.8 x critical. I found it NEAR IMPOSSIBLE to = keep it that way without oil temperature control, or frequent = measurement / re-setup. Oil is messy, attracts dust, creeps over all = surfaces, drowns insects (which then give 'bug quakes') and the = viscosity is strongly temperature dependant. The surface tension also = varies, which can give beam drift.=20 For oil systems, you need to measure the damping for very small = displacements - use your SDR recording programme to monitor and display = this. If you pull the mass 1/2" to one side and then release it, you may = observe a significantly higher damping due to swirl in the oil and the = system may still be under-damped for normal seismic signals.=20 I honestly don't know why anyone would try to use oil damping = these days. EM damping using NdFeB magnets is simple, cheap, clean, easy = to set up and to adjust. For a Lehman, the damping required is also strongly dependant on = the period you choose and hence on the suspension adjustment. You need a = fair range of damping adjustment available. There are two ways of providing electromagnetic damping. You can = either use a flat Al or Cu plate in a pole gap with a strong magnetic = field, or you can use a coil of wire half in the field and put a loading = resistor across it. After having set up the period, you choose a load = resistor (by experiment) which gives near critical damping. This was = done with the cylindrical coils and magnets in the Sprengnether = seismometers. However, the sensitivity then depends on the value of the = damping resistor, which complicates matters.=20 I prefer to keep the damping and sensor coil functions separate. = With two N+S pairs of opposing flat magnets 1" x 1/2" x 1/4" on 1/4" = baseplates, you just move the high central field over a 1/16" to 1/8" = thick Al or copper tongue till you get the desired damping. Electro magnetic damping is far easier to adjust than oil = damping and with the ready availability of strong NdFeB magnets, it is = cheap and simple to implement. Suppliers are Sedona2 on Ebay, Amazing = Magnets (occasional E-Bay), "Emovendo" on ebay only (perhaps the = cheapest N48 supplier), K&J magnetics ( wide range) www.kjmagnetics.com = and www.wondermagnet.com 8. Use as little AMPLIFIER GAIN as possible to avoid clipping on = major events. Most of the files I see on the seismicnet site have been = recorded at far more gain than necessary. You may have to make component = value changes in your amplifier to accomplish this. Agreed, but the practical choice is likely to depend on the = local environmental noise and on the Ocean background. You want to be = able to resolve the background signals at times of "low noise", but you = don't want strong quakes to saturate the sensor. Most amateurs do not = have the option of siting their seismometer in quiet rural area. If you use 'period extending' software, you will need more = amplification to cope with the lower amplitude of the longer period = waves. You are likely to get uncertain readings if you are amplifying = noise. 16 bit A/D converters, with three bits of converter noise, are = not too helpful in this respect. Perhaps we could agree on a rough amplitude for the ocean = background signals?=20 The gain you can use also depends on the noise and resolution in = your A/D Converter. A/D Converter boards with +/-1/2 LSB resolved = internal noise are available. >> Subject: feasible maximum mass for a Lehman seismometer At the risk of ruining a good discussion going on the last = couple of days -- I would like to have some input on what the best / = maximum mass for Lehman horizontal seismometer. The best mass is the lowest which gives you clear low noise = signals. This advice 'begs the question'. The 'kt' thermal excitation noise sets the minimum seismic mass = at about an ounce, so you are better with 1/2 lb, minimum.=20 If you use a solid metal beam, as opposed to a tube or a U = channel, the moment of inertia of the beam can actually reduce the = 'radius of gyration k' of the combined beam + seismic mass, giving a = shorter period than you would get from the seismic mass at the end of a = weightless arm. The beam needs to be light but rigid (aim for a tube = weight less end fittings 1/4 the weight of the seismic mass or less). I = have found the light 1/2" nominal welded stainless steel water pipe to = be very satisfactory. The thermal expansion coefficient matches that of = a piano wire suspension quite well. It is also cheap and you can buy = brass compression fittings on which to mount the suspension, the seismic = mass and the damping components. This makes the construction quite easy. This said, the period of a simple pendulum is independent of the = mass.=20 It is advisable to keep the boom length between 70 cm and 100 = cm. This is because you are using the garden gate type of suspension and = shorter lengths require you to set up the side to side level position = with rapidly increasing precision. This can make a 12" beam not only = exceptionally difficult to adjust, but very sensitive to tilt drift, = either from the suspension system or from natural earth movements. =20 Using a 30/60/90 degree triangle suspension is fine. Try to = keep the boom / wire angle above 20 deg, or the suspension loading will = be large. You can buy nickel coated 8 thou steel wire from a music shop, = for stringing mandolins. To clamp wire, I drill a 1/16" hole just under = the head of a bolt. Then I 'dish' a couple of washers by putting them on = a wood block and hitting the centre hole with a large centre punch + = hammer. You put the two washers on the bolt with the outer cup edges = touching and feed the wire between these edges and through the hole in = the bolt. This gives a good 'edge clamp' on the wire. For adjustment screws, I use stainless steel nuts and bolts = bought from a marine / boat-builder supplier. I drill out the threaded = end of the bolt with a centre drill and stick a stainless ball bearing = in the conical hole. I drill a plain hole in the baseplate and stick a = nut onto the lower side with methacrylate or epoxy cement. It is = essential that the bolt and the nut are made of the same material, or = the adjustment will drift with change in temperature. I usually use a = second nut + a spring washer on the lower side of the mounting nut to = provide tensioning / alignment in the thread. I stick stainless steel = mounting plates onto the concrete floor, either with the special = concrete 'pool adhesive' or with epoxy. If you use epoxy, it is a good = idea to dry out the top of the cement thoroughly with a warm air blower. Lastly: >> Hi gang, There has been some recent discussion about calibrating = seismometers. Several years ago, my article on a calibrator using a = meter movement as a force transducer was put on our 'home' = www.seismic.com. Go to "Build Your Own Seismographic Station" then to = "Article by Bob Barns". ?? Can anyone help me find this article, please? www seismic.com = seems like a huge website with lots of advertising, but only a very old = article on seismology. 'Earth Science' seems to be just advertising = vitamins...=20 If you want a force calibration system with much higher forces = than a meter movement, you can use a small NdFeB cube magnet with a = Maxwell coil. These look similar to a Helmholtz coil, but with double = the winding spacing and the windings connected in opposition. This gives = a constant field gradient. You can calibrate it using a pendulum of a = known length and mass, by measuring the deflection / coil current. Regards, Chris Chapman
I think we all should petition Chris to write a book on seismometer = construction.  I have learned more from reading his postings than = just=20 about any other source.
 
Larry Conklin
 
 
----- Original Message -----
From:=20 Meredith Lamb
To: psn-l
Sent: Wednesday, July 21, 2004 = 1:16=20 AM
Subject: FW: Re: what is your=20 advice?

 
The following msg is being forwarded and was reply = written=20 by Chris Chapman:
 
Hi=20 All,
 
    A few more comments on = seismometers....
 
HELPFUL HINTS FROM A FUSSY ELDERLY SEISMIC DATA = LOGGER:
1. Be sure that your STATION CO-ORDINATES are correct. You = can use=20 Microsoft Streets and Trips, or online MapQuest for the purpose. = Also=20 align horizontal sensors to true North or East, or else give true=20 direction in sensor comments box.
    OK on the alignment and reporting. Full = details=20 would often be most helpful.
 
     As far as I can see, the Lat/Long = search=20 option has now been removed from = Mapquest. 
 
    The Microsoft Streets and Trips CD only = gives=20 information for the USA and parts of Canada.
 
    Has anyone got a reference for a world = wide map=20 programme which you can use with Lat + Long?
2. LOCK your timing to GPS or WWV or a crystal clock slaved = to=20 WWVB.
    Fine, but it would be helpful if = Larry=20 included a programme which DECODED the WWVB minute long signals = directly and=20 could also update the clock at user defined intervals. WWVB modules = are=20 available. The receive limit is set by local radio interference = /=20 noise, but can be expected to be >2,000 miles at night. Keep = the=20 receiver well away (10 ft +) from a CRT display. = The effective=20 signal coverage is shown at h= ttp://www.boulder.nist.gov/timefreq/stations/wwvbcoverage.htm &n= bsp;
3. CALIBRATE YOUR SENSOR. You would not have much use for a = voltmeter=20 with no scale on it, would you? For open loop sensors, I have two = methods.=20 One uses the raw sensor output of pendulum movement between fixed = stops,=20 the other measures the force exerted by the pendulum in response = to a=20 known current. I can tell you more if you = ask.
    Remembering that seismometers are used = which=20 measure displacement, or velocity or acceleration, so we need = several=20 calibration methods.=20
    Remember also that the signal which you = actually see can depend quite strongly on the local sub surface = geological structures. If you are sitting on a thick layer of water=20 saturated alluvial soil, it can shake much like a jelly. If your = seismometer=20 is calibrated in say volts / metre / sec, you may see some variation = in=20 signal with the reception angle and there may be large errors in the = calculated amplitude / distance measurement. An alternative method = is to=20 measure the recorded amplitude of a series of 'known' quakes and = then make=20 up a rough correlation table. 
4. DO NOT submit files with high sample rates on distant = teleseisms.=20 High frequencies are attenuated with distance, and files with = excessive=20 sample rate only take up bandwidth and archival storage space. = Decimate=20 before submitting. One to five samples per second should handle = most=20 teleseisms without loss of waveform detail. Also, do not cover an = overly=20 large time span after the L wave onset.
      You will have difficulty in = separating out the P and S waves if your system cannot reproduce 0.5 = to 1 Hz=20 quite accurately.=20
    I would suggest that 10 sps is a = more=20 reasonable compromise. Local quakes also have P & = S components=20 of higher frequency.
    Some locations have relatively=20 high damping down to below about 1/2 Hz. If you also have high=20 environmental noise, you may have difficulty in resolving quake = arrival=20 times.
    
5. DO NOT use any more FILTERING than absolutely necessary. = Let some=20 microseisms come through. Leave it to the downloader of files do = more=20 filtering if they wish.
    Sure, but it is helpful if you can at = least=20 recognise the outline of the earthquake signal. I don't find a = seismic=20 signal which completely masked in either high frequency = environmental or in=20 instrument noise, very helpful.
6. If possible, adjust your sensor's NATURAL PERIOD to least = 16=20 seconds if you record and report teleseisms. If that is not = practical, I=20 have written an application program for WinQuake files which can = digitally=20 extend the effective period of your sensor by up to a factor of = five. I=20 use it routinely on my sensors which have natural periods of 5, 8, = and 14=20 seconds to extend their response to 24 = seconds.
   This does depend on what sort of seismometer = you use=20 and on it's natural period. Local environmental noise may become = serious by=20 10 Hz. The Ocean background will give quite large signals somewhere=20 between 2 and 10 seconds, which need to be filtered out. Twin = Tee=20 rejection filters have been used successfully and can give over 50 = dB peak=20 rejection. The frequency and the amplitude may change with = time.
    Using beam type seismometers, it is = desirable=20 to have the period between 20 and 30 seconds. A 10 second to 30 = second range=20 allows good detection of L & R waves. 
    Simple damped pendulum seismometers = with a 1.4=20 sec period are popular in Europe and pickup P & S waves quite=20 nicely.
7. Control your sensor DAMPING. The barest amount of = overshoot on a=20 displaced pendulum is about right.
    I agree, but this is the ONE FACTOR in=20 seismometer construction which is likely to give MOST PROBLEMS. = I found=20 it DIFFICULT to set up an oil damped system to about 0.8 x = critical. I found it NEAR IMPOSSIBLE to keep it that way = without oil=20 temperature control, or frequent measurement / re-setup. Oil is = messy,=20 attracts dust, creeps over all surfaces, drowns insects (which then = give=20 'bug quakes') and the viscosity is strongly temperature = dependant.=20 The surface tension also varies, which can give beam drift.
    For oil systems, you need to measure = the=20 damping for very small displacements - use your SDR recording = programme to=20 monitor and display this. If you pull the mass 1/2" to one side and = then=20 release it, you may observe a significantly higher damping due to = swirl in=20 the oil and the system may still be under-damped for normal seismic = signals.=20
    I honestly = don't=20 know why anyone would try to use oil damping these days. EM damping = using=20 NdFeB magnets is simple, cheap, clean, easy to set up and to=20 adjust.
    For a Lehman, the damping required is = also=20 strongly dependant on the period you choose and = hence on=20 the suspension adjustment. You need a fair range of damping = adjustment=20 available.
    There are two ways of providing = electromagnetic=20 damping. You can either use a flat Al or Cu plate in a pole gap = with a=20 strong magnetic field, or you can use a coil of wire half in = the field=20 and put a loading resistor across it. After having set up the = period,=20 you choose a load resistor (by experiment) which gives near = critical=20 damping. This was done with the cylindrical coils and magnets in the = Sprengnether seismometers. However, the sensitivity then = depends=20 on the value of the damping resistor, which complicates matters. =
    I prefer to keep the damping and sensor = coil=20 functions separate. With two N+S pairs of opposing flat magnets = 1" x=20 1/2" x 1/4" on 1/4" baseplates, you just move the high = central field=20 over a 1/16" to 1/8" thick Al or copper tongue till you get the = desired=20 damping.
    Electro magnetic damping is far easier = to=20 adjust than oil damping and with the ready availability of = strong NdFeB=20 magnets, it is cheap and simple to implement. Suppliers are Sedona2 = on Ebay,=20 Amazing Magnets (occasional E-Bay), = "Emovendo" on=20 ebay only (perhaps the cheapest = N48=20 supplier), K&J magnetics ( wide range) www.kjmagnetics.com  = and www.wondermagnet.com
 
8. Use as little AMPLIFIER GAIN as possible to avoid = clipping on=20 major events. Most of the files I see on the seismicnet site have = been=20 recorded at far more gain than necessary. You may have to make = component=20 value changes in your amplifier to accomplish this.
 
     Agreed, but the practical = choice is=20 likely to depend on the local environmental noise and on the Ocean=20 background. You want to be able to resolve the background signals at = times=20 of "low noise", but you don't want strong quakes to saturate the=20 sensor. Most amateurs do not have the option of siting their=20 seismometer in quiet rural area.
    If you use 'period extending' software, = you=20 will need more amplification to cope with the lower amplitude of the = longer=20 period waves. You are likely to get uncertain readings if you are = amplifying=20 noise. 16 bit A/D converters, with three bits of converter noise, = are not=20 too helpful in this respect.
    Perhaps we could agree on a rough = amplitude for=20 the ocean background signals?
    The gain you can use also depends on = the noise=20 and resolution in your A/D Converter. A/D Converter boards with = +/-1/2 LSB=20 resolved internal noise are available.
 
>>    Subject: feasible = maximum=20 mass for a Lehman seismometer
    At the risk of ruining a good = discussion=20 going on the last couple of days -- I would like to have some input = on what=20 the best / maximum mass for Lehman horizontal = seismometer.

     The best mass=20 is the lowest which gives you clear low noise signals. This = advice=20 'begs the question'.
    The 'kt' = thermal=20 excitation noise sets the minimum seismic mass at about an ounce, so = you are=20 better with 1/2 lb, minimum. 
    If you use = a solid=20 metal beam, as opposed to a tube or a U channel, the moment of = inertia of=20 the beam can actually reduce the 'radius of gyration k' of the = combined=20 beam + seismic mass, giving a shorter period than you would get = from the=20 seismic mass at the end of a weightless arm. The beam = needs to be=20 light but rigid (aim for a tube weight less end fittings 1/4 the = weight of=20 the seismic mass or less). I have found the light 1/2" nominal = welded=20 stainless steel water pipe to be very satisfactory. The thermal = expansion=20 coefficient matches that of a piano wire suspension quite = well. It is=20 also cheap and you can buy brass compression fittings on which to = mount the=20 suspension, the seismic mass and the damping components. This makes = the=20 construction quite easy.
    This said, the period of a = simple=20 pendulum is independent of the mass.
    It is advisable to keep the boom length = between=20 70 cm and 100 cm. This is because you are using the garden gate type = of=20 suspension and shorter lengths require you to set up the side to = side level=20 position with rapidly increasing precision. This can make a 12" beam = not=20 only exceptionally difficult to adjust, but very sensitive to = tilt=20 drift, either from the suspension system or from natural earth = movements.=20  
     Using a 30/60/90 degree triangle=20 suspension is fine. Try to keep the boom / wire angle above 20 deg, = or the=20 suspension loading will be large. You can buy nickel coated 8 thou = steel=20 wire from a music shop, for stringing mandolins. To clamp wire, I = drill a=20 1/16" hole just under the head of a bolt. Then I 'dish' a couple of = washers=20 by putting them on a wood block and hitting the centre hole with a = large=20 centre punch + hammer. You put the two washers on the bolt with the = outer=20 cup edges touching and feed the wire between these edges and through = the=20 hole in the bolt. This gives a good 'edge clamp' on the = wire.
    For adjustment screws, I use stainless = steel=20 nuts and bolts bought from a marine / boat-builder supplier. I drill = out the=20 threaded end of the bolt with a centre drill and stick a = stainless ball=20 bearing in the conical hole. I drill a plain hole in the baseplate = and stick=20 a nut onto the lower side with methacrylate or epoxy = cement. It is=20 essential that the bolt and the nut are made of the same material, = or the=20 adjustment will drift with change in temperature. I usually use a = second nut=20 + a spring washer on the lower side of the mounting nut to provide=20 tensioning / alignment in the thread. I stick stainless steel = mounting=20 plates onto the concrete floor, either with the special = concrete 'pool=20 adhesive' or with epoxy. If you use epoxy, it is a good idea to dry = out the=20 top of the cement thoroughly with a warm air blower.
 
Lastly:
>> Hi gang,
  There has been some recent discussion about calibrating=20 seismometers.    Several years ago, my article on a=20 calibrator using a meter movement as a force transducer was put on = our=20 'home'  www.seismic.com.  Go to "Build Your Own=20 Seismographic Station" then to "Article by Bob Barns".
 
    ?? Can anyone help me find this = article,=20 please? www seismic.com seems like a huge website with lots of = advertising,=20 but only a very old article on seismology. 'Earth Science' = seems to be=20 just advertising vitamins...
 
    If you want a force calibration system = with=20 much higher forces than a meter movement, you can use a small NdFeB = cube=20 magnet with a Maxwell coil. These look similar to a Helmholtz = coil, but=20 with double the winding spacing and the windings connected in=20 opposition. This gives a constant field gradient. You can calibrate = it using=20 a pendulum of a known length and mass, by measuring the = deflection /=20 coil current.
 
    Regards,
 
    Chris=20 = Chapman
<= /HTML> Subject: Re: FW: Re: what is your advice? From: John or Jan Lahr johnjan@........ Date: Wed, 21 Jul 2004 09:34:22 -0600
At 11:16 PM 7/20/2004, Chris C. wrote:
As far as I can see, the Lat/Long search option has now been removed from Mapquest.
 
    The Microsoft Streets and Trips CD only gives information for the USA and parts of Canada.
 
    Has anyone got a reference for a world wide map programme which you can use with Lat + Long?

I've listed four web sites that will help in finding coordinates:
http://jclahr.com/science/psn/coordinates/

Only one includes any coverage outside of the US, and that is http://terraserver.com/ .
Unfortunately they have started limiting the resolution of their free images, and they do
not have complete global coverage.

If anyone knows of any other sites from which ones coordinates can be determined,
please let me know and I'll add a link to my site.

Cheers,
John Lahr

Subject: Re: FW: Re: what is your advice? From: "Larry Conklin" lconklin@............ Date: Wed, 21 Jul 2004 11:54:56 -0400 Another very good mapping program that includes Lat/Lon measuring = capability is the Delorme Street Atlas USA. It is a great program and = well worth the price, but like the Microsoft program it covers the US = only. Larry Conklin ----- Original Message -----=20 From: John or Jan Lahr=20 To: psn-l@................. Sent: Wednesday, July 21, 2004 11:34 AM Subject: Re: FW: Re: what is your advice? At 11:16 PM 7/20/2004, Chris C. wrote: As far as I can see, the Lat/Long search option has now been removed = from Mapquest.=20 =20 The Microsoft Streets and Trips CD only gives information for = the USA and parts of Canada.=20 =20 Has anyone got a reference for a world wide map programme which = you can use with Lat + Long? I've listed four web sites that will help in finding coordinates: http://jclahr.com/science/psn/coordinates/=20 Only one includes any coverage outside of the US, and that is = http://terraserver.com/ . Unfortunately they have started limiting the resolution of their free = images, and they do not have complete global coverage. If anyone knows of any other sites from which ones coordinates can be = determined, please let me know and I'll add a link to my site. Cheers, John Lahr
Another very good mapping program that includes = Lat/Lon=20 measuring capability is the Delorme Street Atlas USA.  It is a = great=20 program and well worth the price, but like the Microsoft program it = covers the=20 US only.
 
Larry Conklin
----- Original Message -----
From:=20 John or = Jan Lahr=20
Sent: Wednesday, July 21, 2004 = 11:34=20 AM
Subject: Re: FW: Re: what is = your=20 advice?


At 11:16 PM 7/20/2004, Chris C. wrote:
As far as I can see, = the Lat/Long=20 search option has now been removed from Mapquest.=20
 
    The Microsoft Streets and Trips CD = only=20 gives information for the USA and parts of Canada.=20
 
    Has anyone got a reference for a = world wide=20 map programme which you can use with Lat + = Long?

I've listed=20 four web sites that will help in finding coordinates:
http://jclahr.com/science/psn/coordinates/ =

Only=20 one includes any coverage outside of the US, and that is http://terraserver.com/=20 .
Unfortunately they have started limiting the resolution of their = free=20 images, and they do
not have complete global coverage.

If = anyone=20 knows of any other sites from which ones coordinates can be=20 determined,
please let me know and I'll add a link to my=20 site.

Cheers,
John Lahr

Subject: Re: FW: Re: what is your advice? From: Mark Robinson mark.robinson@............... Date: Thu, 22 Jul 2004 07:05:35 +1200 > If anyone knows of any other sites from which ones coordinates can be > determined, > please let me know and I'll add a link to my site. > > Cheers, > John Lahr > www.heavens-above.com isn't so much a terrestrial atlas, but it does include a rather comprehensive database of lat/long. Your local authority may have this information available at the end of the phone. regards all Mark Robinson ------------- 22 Jul 1839 52nd and last chief sign Declaration of Independence: Ko Te Tiriti Mana Motuhake Maori Tuatahi. 22 Jul 1914 May Palmer attended the first Public Service Association annual dinner as "ladies representative". 22 Jul 1950 U.S. Census Bureau says there are 150 million people in the U.S. 22 Jul 1991 A Greek oil tankers splits off Australia. 22 Jul 1995 HMNZS Charles Upham breaks her moorings in heavy weather and damages the Tui. A tornado damages houses and trees in Pakuranga. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Fw: A Sun story from Jim ODonnell From: "Larry Cochrane" lcochrane@.............. Date: Sat, 24 Jul 2004 00:18:49 -0700 FYI.... -Larry > Jim ODonnell (jimo17@......... thought you might be interested in this > Las Vegas Sun (http://www.lasvegassun.com/) story: > > http://www.lasvegassun.com/sunbin/stories/sun/2004/jul/23/517223540.html > > Message from sender: > It is a shaky business but some has to do it! > > ================================================================== > > Valley's ground could make quakes worse > > By Beth Slovic > LAS VEGAS SUN > > The ground in the Las Vegas Valley could increase the power of an earthquake should the "big one" every hit, according to a new study of seismic activity in Southern Nevada. > > A team of researchers spent two years studying eight known faults in the valley and found that a major earthquake would leave significant damage here, although scientists said such a quake was unlikely in the near future. > > The study, conducted by a group of researchers from UNLV, University of Nevada, Reno, and Lawrence Livermore National Laboratory in California, is is the first major study of the faults in the valley in more than a decade and showed how the ground would react in an earthquake, a key factor in what kind of damage an earthquake would do. > > The research found that the ground is less stable than previously thought and more prone to shaking in the event of an earthquake, particularly in the northeast part of the valley. > > The ground could also amplify the magnitude of an earthquake here, even one that registers at a lower number on the Richter scale outside the valley. > > "Basins (like the Las Vegas Valley) shake by factors of 10 when an earthquake passes through them," said Jim O'Donnell, a geophysicist and a member of the Nevada Earthquake Safety Council who has monitored the data collected from the study. "A magnitude 5 earthquake elsewhere would be like a 6 here." > > Cathy Snelson, a University of Nevada Las Vegas seismologist who led a portion of the two-year study, said that while Nevada is among the most seismically active states in the nation, the valley doesn't see many earthquakes. > > Snelson said a "major event" is not likely and said while there's no anecdotal evidence of such a quake in the last 100 years. But she said there's "a lot of potential here for damage." > > Scientists are not very good at predicting earthquakes, O'Donnell said. > > "We may not have one tomorrow, but we could have one at anytime," O'Donnell said. > > Snelson noted the last noticeable earthquake in the valley was a 3.5 magnitude earthquake in 2001, which was centered on the west side. She called it small, but because of the ground it was felt across the valley. > > Of the eight known faults in the valley, one runs directly under the Strip at its southern edge, which could cause a great deal of structural damage to buildings and casualties if the earthquake hit at least 5.9 on the Richter scale, O'Donnell said. > > "There will be a lot of shaking going on on the Strip if the focal point of the earthquake is near those faults running under it," he said. "We're not in a high seismic area, but were are at high risk for damage; we have the potential for magnitude 6 or 7 earthquake that could look like a 7 or 8." > > For the first time since 1992, when the Energy Department removed several instruments from the valley that were used to monitor explosions at the Nevada Test Site, seismographs were used to monitor movement in the earth's crust in the valley. > > That's an important achievement in a fast-growing city where new buildings are being built every day, said O'Donnell. > > A 2001 estimate using software from the Federal Emergency Management Agency revealed that a 6.9 magnitude earthquake here could cause $11 billion in economic losses and thousands of deaths. > > That, in part, is because the Las Vegas Valley's geological structure acts like a bowl of jelly, Snelson said. > > Even a "short and sweet" earthquake here could send strong ripples through the sediment that sits inside the bowl, shaking the Las Vegas Valley at varying degrees of severity depending on the earth's firmness at the different locations, Snelson said. > > In August 2003, Snelson and several of her university colleagues set off a series of underground explosions designed to mimic seismic activity. The experiment was designed to help geologists map the subsurface of the valley. > > After several months analyzing the data her team collected, Snelson's group determined that the types of rocks in some parts of the valley are less stable and would be more prone to shaking in the event of an earthquake. > > As a result, the scientists determined that the northeastern portion of the valley would feel the effects of an earthquake more intensely than the southwestern area would. But the likelihood of a major earthquake in the valley is low, she added. > > In explaining why an earthquake isn't likely, Wanda Taylor, a UNLV geologist with the project, said the interval between earthquakes is typically thousands of years. > > Though it would be possible to determine when earthquakes last shook the various known fault lines in the Valley, geologists here have not had the funding to do that yet, Taylor said. > > But using something called fault scrapes on some of the fault lines Taylor estimated that the most recent earthquakes happened recently enough that they likely would not re-occur in the near future. > > Single-family homes with wood frames would be less vulnerable to earthquakes than large steel structures like hotels along the Strip, Snelson said. > > Nonetheless, residents should prepare their families for an earthquake emergency, she said. > > Helping Las Vegas and its public officials better prepare for a potential earthquake is one goal of the scientists' work. > > Currently, only 17 seismographs monitor seismic activity across the valley. For geologists to better predict when an earthquake may occur, they need more equipment Snelson said. > > Nevada is the third most seismically active state, after Alaska and California, Snelson said. Most Silver State earthquakes have happened in the northern part of Nevada, but the potential for large-scale damage exists in the south, where more people live, she said. > > Ron Lynn, Clark County's Building Services director, said new buildings in Las Vegas follow the International Building Code for the year 2000, and he said the building standards included earthquake regulations that were fairly strict. > > Gathering new information on earthquakes is key to setting better building code standards, he said. > > "This valley has been under-analyzed," said Lynn, who is also the chairman of the Nevada Earthquake Safety Council, referring to the area's seismic history. "We are only now starting to get information." > > Rather than worry about earthquakes, however, people should prepare, Snelson said. > > "People in California live with this all their lives," she said. "They don't stop living, nor should we." > > > ================================================================== > > ____ VEGAS.COM: THE OFFICIAL VEGAS TRAVEL SITE ____ > > To Do Vegas Right, It's Who You Know. > And nobody's knows Vegas like VEGAS.com. > The next time you plan your trip, > use VEGAS.com to: > > * Book a room: http://www.vegas.com > * Book an air/hotel package: http://www.vegas.com/travel/ > * Book a tour: http://shop.vegas.com/tours/ > * Book a show: http://www.vegas.com/shows/ > * Buy a nightclub pass: http://www.vegas.com/nightclubs/ > * Book a tee time: http://www.vegas.com/golf/ > * Make dinner reservations: http://www.vegas.com/restaurant/ > * Attractions: http://www.vegas.com/attractions/ > * Great travel tips: http://www.vegas.com/traveltips/ > > ================================================================== > > Contents copyright 2004 Las Vegas Sun, Inc. > > You are receiving this e-mail because a friend or acquaintance > sent it to you. If you no longer want to receive these messages, > please contact the sender, not the Las Vegas Sun. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: ebay auction From: BOB BARNS royb1@........... Date: Wed, 28 Jul 2004 13:54:13 -0400 Hi gang, SEISMOGRAPH scientific instrument by GEOMETRICS nr Item number: 2259633751 ends Aug. 2 Bob Barns __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: ebay auction From: "Doug Crice" dcrice@............ Date: Wed, 28 Jul 2004 11:45:42 -0700 This is an exploration seismograph (not an earthquake seismograph) designed for refraction surveys using a sledgehammer as an energy source. This type of instrument is commonly used to map subsurface geology (e.g. depth to bedrock) down to a maximum of 30 meters. It looks like everything is there except the aluminum striker plate and of course a sledgehammer. Read about refraction surveys here ftp://geom.geometrics.com/pub/seismic/Literature/s-tr2.pdf Doug Crice Geostuff http://www.georadar.com/geostuff.htm 12996 Somerset Drive phone 1-530-274-4445 Grass Valley, CA 95945 USA fax 1-530-274-4446 -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... On Behalf Of BOB BARNS Sent: Wednesday, July 28, 2004 10:54 AM To: psn mail Subject: ebay auction Hi gang, SEISMOGRAPH scientific instrument by GEOMETRICS nr Item number: 2259633751 ends Aug. 2 Bob Barns __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: ebay auction From: BOB BARNS royb1@........... Date: Wed, 28 Jul 2004 20:09:59 -0400 Doug, Thanks for taking the time to characterize these things. Could it be used to find subsurface water? Bob Barns PS:The "photo of borehole geophones" on your website did not come up for me. Doug Crice wrote: > This is an exploration seismograph (not an earthquake seismograph) designed > for refraction surveys using a sledgehammer as an energy source. This type > of instrument is commonly used to map subsurface geology (e.g. depth to > bedrock) down to a maximum of 30 meters. It looks like everything is there > except the aluminum striker plate and of course a sledgehammer. > > Read about refraction surveys here > ftp://geom.geometrics.com/pub/seismic/Literature/s-tr2.pdf > > Doug Crice > Geostuff http://www.georadar.com/geostuff.htm > 12996 Somerset Drive phone 1-530-274-4445 > Grass Valley, CA 95945 USA fax 1-530-274-4446 > > > -----Original Message----- > From: psn-l-request@.............. [mailto:psn-l-request@............... On > Behalf Of BOB BARNS > Sent: Wednesday, July 28, 2004 10:54 AM > To: psn mail > Subject: ebay auction > > Hi gang, > SEISMOGRAPH scientific instrument by GEOMETRICS nr Item > number: > 2259633751 > ends Aug. 2 > Bob Barns > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > > __________ NOD32 1.825 (20040728) Information __________ > > This message was checked by NOD32 antivirus system. > http://www.nod32.com > > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: ebay auction From: "Doug Crice" dcrice@............ Date: Wed, 28 Jul 2004 17:25:48 -0700 Refraction surveys determine the depth and P wave velocities of = materials. As a general rule, when you hit the water table, the velocity is 5000 ft/sec. Though other materials can have the same velocity, it's = typically water table and that becomes one of the layers. However, you need to work a little harder if you're siting a water well. = You would be more interested in the bedrock contours or fracture zones, and = it might be good to mix in some electrical methods as well. Doug Crice Geostuff http://www.georadar.com/geostuff.htm 12996 Somerset Drive phone 1-530-274-4445 Grass Valley, CA 95945 USA fax 1-530-274-4446 =20 -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@............... = On Behalf Of BOB BARNS Sent: Wednesday, July 28, 2004 5:10 PM To: psn-l@.............. Subject: Re: ebay auction Doug, Thanks for taking the time to characterize these things. Could it be = used to find subsurface water? Bob Barns PS:The "photo of borehole geophones" on your website did not come up=20 for me. Doug Crice wrote: > This is an exploration seismograph (not an earthquake seismograph) designed > for refraction surveys using a sledgehammer as an energy source. This = type > of instrument is commonly used to map subsurface geology (e.g. depth = to > bedrock) down to a maximum of 30 meters. It looks like everything is = there > except the aluminum striker plate and of course a sledgehammer. >=20 > Read about refraction surveys here > ftp://geom.geometrics.com/pub/seismic/Literature/s-tr2.pdf >=20 > Doug Crice > Geostuff http://www.georadar.com/geostuff.htm > 12996 Somerset Drive phone 1-530-274-4445 > Grass Valley, CA 95945 USA fax 1-530-274-4446 > =20 >=20 > -----Original Message----- > From: psn-l-request@.............. = [mailto:psn-l-request@............... On > Behalf Of BOB BARNS > Sent: Wednesday, July 28, 2004 10:54 AM > To: psn mail > Subject: ebay auction >=20 > Hi gang, > SEISMOGRAPH scientific instrument by GEOMETRICS nr Item > number:=20 > 2259633751=09 > ends Aug. 2 > Bob Barns >=20 > __________________________________________________________ >=20 > Public Seismic Network Mailing List (PSN-L) >=20 > To leave this list email PSN-L-REQUEST@.............. with=20 > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. >=20 >=20 > __________________________________________________________ >=20 > Public Seismic Network Mailing List (PSN-L) >=20 > To leave this list email PSN-L-REQUEST@.............. with=20 > the body of the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. >=20 > __________ NOD32 1.825 (20040728) Information __________ >=20 > This message was checked by NOD32 antivirus system. > http://www.nod32.com >=20 >=20 >=20 __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: easy auctions From: BOB BARNS royb1@........... Date: Fri, 30 Jul 2004 11:17:16 -0400 Hi, Everyone has things stashed in dead storage in their house which can be converted to cash with almost no effort. (Better than putting it out on the curb.) I have sold about 170 items on ebay and often received much more than I had estimated;ebay has an enormous audience with seemingly unlimited disposable cash. Selling on ebay is somewhat involved;take good digital pictures, write an attractive ad, go thru all the input questions on ebay, deal with possible questions by email, provide a convenient way for the buyer to pay and finally pack and ship the item. **You can now sell your stuff by simply dropping off the item at the UPS store in Berk. Hts., New Prov., Scotch Pls. Westfield and many other locations all over the US.** You can read about the locations and the details of the process at http://auctiondrop.com Briefly, the item should have an estimated value of $75 or more (I don't know who makes this estimate) and it must weigh less than 20 lbs. I looked at several of their ads on ebay and they do an excellant job of taking the photos, describing the item and presenting it in the ad. (To see some examples, you can search ebay by seller name "auctiondrop".) Their min. commission is $20;they take a certain percentage of the selling price--you get the rest. If you try this, I would like to hear about how it worked out. Bob __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: easy auctions From: Raul Alvarez ralvarez@........ Date: Sat, 31 Jul 2004 06:49:00 -0600 Hi Bob and others, I went to Auctiondrops's website and was shocked! 38% commission + 2.9 "transaction fee" + eBay's fees. Wow, what a rip off! Comes to about 45% in fees! To make matters worse, they start the auction at $1, so if it doesn't make much you owe them the $19.99 minimum + transaction fee + eBay fee! They can't loose. Also noticed they only want the "cream" items - easy to sell, pack and ship. I've been on eBay for almost 5 years now with 1,000's of items. It's quite simple to use their basic services. All you need is a digital camera and a few minutes - you don't really need any special software or hosting site, unless you want to fancy up your ads. And best of all - you are in control of your items. Seems scary to drop off your stuff at UPS, and hope all goes well. Well, that's my 4 cents worth - inflation, you know. :-D Raul BOB BARNS wrote: > Hi, > Everyone has things stashed in dead storage in their house which can > be converted to cash with almost no effort. (Better than putting it > out on the curb.) > I have sold about 170 items on ebay and often received much more than > I had estimated;ebay has an enormous audience with > seemingly unlimited disposable cash. > Selling on ebay is somewhat involved;take good digital pictures, > write an attractive ad, go thru all the input questions on > ebay, deal with possible questions by email, provide a convenient way > for the buyer to pay and finally pack and ship the > item. > **You can now sell your stuff by simply dropping off the item at the > UPS store in Berk. Hts., New Prov., Scotch Pls. > Westfield and many other locations all over the US.** > You can read about the locations and the details of the process at > http://auctiondrop.com > Briefly, the item should have an estimated value of $75 or more (I > don't know who makes this estimate) and it must weigh less > than 20 lbs. > I looked at several of their ads on ebay and they do an excellant > job of taking the photos, describing the item and > presenting it in the ad. (To see some examples, you can search ebay > by seller name "auctiondrop".) > Their min. commission is $20;they take a certain percentage of the > selling price--you get the rest. > If you try this, I would like to hear about how it worked out. > Bob > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with the body of > the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: easy auctions From: BOB BARNS royb1@........... Date: Sat, 31 Jul 2004 10:47:46 -0400 Raul, My notice was to inform those who would like to realize some money from otherwise useless items and do not want to bother with the usual process. I think your characterization of the service as a "rip off" ignores the realities of providing a service like this. They obviously have to make a profit or get out of the business. I'm a little surprized that they will handle an item for as little as $20. It takes me at least 2 hrs. to do a whole auction. If my time is worth $30/hr., this is at least $60. Your having done "1000's" of items shows that you must have a better process than I do, but I suspect that I'm more representative of the "common man". Bob Raul Alvarez wrote: > Hi Bob and others, > > I went to Auctiondrops's website and was shocked! 38% commission + 2.9 > "transaction fee" + eBay's fees. > Wow, what a rip off! Comes to about 45% in fees! To make matters > worse, they start the auction at $1, so if it doesn't make much you owe > them the $19.99 minimum + transaction fee + eBay fee! They can't loose. > Also noticed they only want the "cream" items - easy to sell, pack and > ship. > > I've been on eBay for almost 5 years now with 1,000's of items. It's > quite simple to use their basic services. All you need is a digital > camera and a few minutes - you don't really need any special software or > hosting site, unless you want to fancy up your ads. And best of all - > you are in control of your items. Seems scary to drop off your stuff at > UPS, and hope all goes well. > > Well, that's my 4 cents worth - inflation, you know. :-D > > Raul > > > > BOB BARNS wrote: > >> Hi, >> Everyone has things stashed in dead storage in their house which can >> be converted to cash with almost no effort. (Better than putting it >> out on the curb.) >> I have sold about 170 items on ebay and often received much more than >> I had estimated;ebay has an enormous audience with >> seemingly unlimited disposable cash. >> Selling on ebay is somewhat involved;take good digital pictures, >> write an attractive ad, go thru all the input questions on >> ebay, deal with possible questions by email, provide a convenient way >> for the buyer to pay and finally pack and ship the >> item. >> **You can now sell your stuff by simply dropping off the item at the >> UPS store in Berk. Hts., New Prov., Scotch Pls. >> Westfield and many other locations all over the US.** >> You can read about the locations and the details of the process at >> http://auctiondrop.com >> Briefly, the item should have an estimated value of $75 or more (I >> don't know who makes this estimate) and it must weigh less >> than 20 lbs. >> I looked at several of their ads on ebay and they do an excellant >> job of taking the photos, describing the item and >> presenting it in the ad. (To see some examples, you can search ebay >> by seller name "auctiondrop".) >> Their min. commission is $20;they take a certain percentage of the >> selling price--you get the rest. >> If you try this, I would like to hear about how it worked out. >> Bob >> >> __________________________________________________________ >> >> Public Seismic Network Mailing List (PSN-L) >> >> To leave this list email PSN-L-REQUEST@.............. with the body of >> the message (first line only): unsubscribe >> See http://www.seismicnet.com/maillist.html for more information. >> > > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with the body of > the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > > __________ NOD32 1.828 (20040730) Information __________ > > This message was checked by NOD32 antivirus system. > http://www.nod32.com > > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: easy auctions From: ChrisAtUpw@....... Date: Sat, 31 Jul 2004 13:44:43 EDT In a message dated 31/07/2004, royb1@........... writes: Raul, My notice was to inform those who would like to realize some money from otherwise useless items and do not want to bother with the usual process. I think your characterization of the service as a "rip off" ignores the realities of providing a service like this. They obviously have to make a profit or get out of the business. I'm a little surprized that they will handle an item for as little as $20. It takes me at least 2 hrs. to do a whole auction. If my time is worth $30/hr., this is at least $60. Your having done "1000's" of items shows that you must have a better process than I do, but I suspect that I'm more representative of the "common man". Bob Look at their first advert! For a SLR camera, the bid was $2705, but the seller only got $1905. That is a charge of $800 total. The commission charge is 38% on the first $200 30% on the next $200 20% on the remainder With a min charge of $19.99 Plus Sales Commission on the whole amount 5.25% of the first $25 2.75% of the next $975 ($25.01-$1000) 1.5% of the remaining amount (over $1000) Plus a 2.9% transaction fee on the whole amount. Bob may regard this as acceptable and good value. I just wonder what level of charge ''the common man'' would be regard as ''HIGH''? Thanks for the warning. Regards, Chris
In a message dated 31/07/2004, royb1@........... writes:
<= FONT=20 style=3D"BACKGROUND-COLOR: transparent" face=3DArial=20 color=3D#000000>Raul,
   My notice was to inform those who wo= uld=20 like to realize some money
from otherwise useless items and do not wan= t to=20 bother with the usual
process.
   I think your=20 characterization of the service as a "rip off" ignores
the realities o= f=20 providing a service like this.  They obviously have to
make a pro= fit=20 or get out of the business.  I'm a little surprized that
they wil= l=20 handle an item for as little as $20.
   It takes me at least=20= 2=20 hrs. to do a whole auction.  If my time is
worth $30/hr., this is= at=20 least $60.  Your having done "1000's" of items
shows that you mus= t=20 have a better process than I do, but I suspect that
I'm more=20 representative of the "common man".
Bob
    Look at their first advert!=20 For a SLR camera, the bid was $2705, but the seller only got $1905. = That=20 is a charge of $800 total.
 
    The commission charge is 38% on the first=20 $200
    30% on the next $200
    20% on the remainder
    With a min charge of $19.99
 
Plus Sales Commission on the whole amount
    =20
5.25% of the first $25<= BR>2.75% of the next $975 ($25.01-$1000)
1.5% of the remaining amount (over $1000)

= Plus a=20 2.9% transaction fee on the whole amount.
 
    Bob may regard this as=20 acceptable and good value.
    I just wonder what level o= f=20 charge ''the common man'' would be regard as ''HIGH''?
 
    Thanks for the=20 warning.
    
    Regards,
 
    Chris
 
=20
Subject: Re: easy auctions From: Raul Alvarez ralvarez@........ Date: Sat, 31 Jul 2004 12:19:44 -0600 Hi Bob, Sorry that you disagree with me. Guess my opinion about their fees comes from a lifetime of "DIY'ing". I strongly believe that people should be self sufficient. In my 60 years, I have always done all my automotive, plumbing, electrical and other repairs, built three homes by myself, and so on. When you don't have much, it's hard to give it to someone when you can just do the work rather than pay to have it done. You said it takes two hours to do a whole auction. Do you mean ONE item or a group of items? Also consider that they only want "easy" stuff to sell - check their list of items accepted. For example, 45% of, say, a $500 sale is $225. That's a 7.5 hours of work at the rate you quoted! Just look at the examples and what they are selling right now. Sure wish I could make that kind of profit for placing just one item on eBay. BTW, to answer your question about my process. I do not use any of the auction services or software - just need to have more control I guess. I generated a template with "Dreamwever" - an HTML generator. Then I just plug in the ad text details and pictures. Copy and paste this to the ebay posting page and it's done. Again, sorry if it upset you. Raul BOB BARNS wrote: > Raul, > My notice was to inform those who would like to realize some money > from otherwise useless items and do not want to bother with the usual > process. > I think your characterization of the service as a "rip off" ignores > the realities of providing a service like this. They obviously have > to make a profit or get out of the business. I'm a little surprized > that they will handle an item for as little as $20. > It takes me at least 2 hrs. to do a whole auction. If my time is > worth $30/hr., this is at least $60. Your having done "1000's" of > items shows that you must have a better process than I do, but I > suspect that I'm more representative of the "common man". > Bob > > > > Raul Alvarez wrote: > >> Hi Bob and others, >> >> I went to Auctiondrops's website and was shocked! 38% commission + >> 2.9 "transaction fee" + eBay's fees. >> Wow, what a rip off! Comes to about 45% in fees! To make matters >> worse, they start the auction at $1, so if it doesn't make much you >> owe them the $19.99 minimum + transaction fee + eBay fee! They can't >> loose. >> Also noticed they only want the "cream" items - easy to sell, pack >> and ship. >> >> I've been on eBay for almost 5 years now with 1,000's of items. It's >> quite simple to use their basic services. All you need is a digital >> camera and a few minutes - you don't really need any special software >> or hosting site, unless you want to fancy up your ads. And best of >> all - you are in control of your items. Seems scary to drop off your >> stuff at UPS, and hope all goes well. >> >> Well, that's my 4 cents worth - inflation, you know. :-D >> >> Raul >> >> > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: easy auctions From: BOB BARNS royb1@........... Date: Sat, 31 Jul 2004 20:30:46 -0400 Hi Raul, First, I am enjoying the exchanges of viewpoint on this;I am not upset in the least. Your ability to do all these things for yourself is admirable but VERY unusual. I have also done some, for example, I replaced the crankshaft in a car--twice! (The second time was not necessitated by poor workmanship on the first instance.) :-) I have several friends who might be interested in realizing a few bucks from unwanted things but who are totally incapable of using ebay. For example, they have no digital camera. One friend is simply afraid of putting up an auction. My posting was intended to help this sort of person. Bob Raul Alvarez wrote: > Hi Bob, > > Sorry that you disagree with me. Guess my opinion about their fees > comes from a lifetime of "DIY'ing". I strongly believe that people > should be self sufficient. In my 60 years, I have always done all my > automotive, plumbing, electrical and other repairs, built three homes by > myself, and so on. When you don't have much, it's hard to give it to > someone when you can just do the work rather than pay to have it done. > You said it takes two hours to do a whole auction. Do you mean ONE item > or a group of items? Also consider that they only want "easy" stuff to > sell - check their list of items accepted. For example, 45% of, say, a > $500 sale is $225. That's a 7.5 hours of work at the rate you quoted! > Just look at the examples and what they are selling right now. > Sure wish I could make that kind of profit for placing just one item on > eBay. BTW, to answer your question about my process. I do not use any of > the auction services or software - just need to have more control I > guess. I generated a template with "Dreamwever" - an HTML generator. > Then I just plug in the ad text details and pictures. Copy and paste > this to the ebay posting page and it's done. > > Again, sorry if it upset you. > > Raul > > BOB BARNS wrote: > >> Raul, >> My notice was to inform those who would like to realize some money >> from otherwise useless items and do not want to bother with the usual >> process. >> I think your characterization of the service as a "rip off" ignores >> the realities of providing a service like this. They obviously have >> to make a profit or get out of the business. I'm a little surprized >> that they will handle an item for as little as $20. >> It takes me at least 2 hrs. to do a whole auction. If my time is >> worth $30/hr., this is at least $60. Your having done "1000's" of >> items shows that you must have a better process than I do, but I >> suspect that I'm more representative of the "common man". >> Bob >> >> >> >> Raul Alvarez wrote: >> >>> Hi Bob and others, >>> >>> I went to Auctiondrops's website and was shocked! 38% commission + >>> 2.9 "transaction fee" + eBay's fees. >>> Wow, what a rip off! Comes to about 45% in fees! To make matters >>> worse, they start the auction at $1, so if it doesn't make much you >>> owe them the $19.99 minimum + transaction fee + eBay fee! They can't >>> loose. >>> Also noticed they only want the "cream" items - easy to sell, pack >>> and ship. >>> >>> I've been on eBay for almost 5 years now with 1,000's of items. It's >>> quite simple to use their basic services. All you need is a digital >>> camera and a few minutes - you don't really need any special software >>> or hosting site, unless you want to fancy up your ads. And best of >>> all - you are in control of your items. Seems scary to drop off your >>> stuff at UPS, and hope all goes well. >>> >>> Well, that's my 4 cents worth - inflation, you know. :-D >>> >>> Raul >>> >>> >> > > > __________________________________________________________ > > Public Seismic Network Mailing List (PSN-L) > > To leave this list email PSN-L-REQUEST@.............. with the body of > the message (first line only): unsubscribe > See http://www.seismicnet.com/maillist.html for more information. > > __________ NOD32 1.828 (20040730) Information __________ > > This message was checked by NOD32 antivirus system. > http://www.nod32.com > > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Bullen book on ebay From: BOB BARNS royb1@........... Date: Fri, 06 Aug 2004 09:43:48 -0400 Hi gang, Bullen's book can be bought on ebay-- INTRODUCTION TO THE THEORY OF SEISMOLOGY-Bullen, K.E. Item number: 6916993254 Starting price is $8 and the auction ends 8/10 Bob Barns __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: mystery stations? From: sismos@.............. Date: Thu, 12 Aug 2004 06:27:43 -0400 Hello Everyone, I got a note from a researcher in Nicaragua wondering if I anyone recognizes and has any information about these stations GSV Goldstream Valley -147.937 64.9216 302.8 GSVT Goldstream Valley - Tok -142.9821 63.3372 497 OMCO Orchard Mesa -108.517 39.027 0 PSDMA Soufriere -61.357 15.235 60 PSDMB Cotton Hill -61.457 15.585 40 PSDMZ Portsmouth -61.4563 15.577 0 He wants to know 1 Type of senor 2 Is the station in operation 3 Type of station 4 Is there volcanic activity near by 5 Is that data available I will be traveling for the next two weeks but will try to check my mail. The guys is: Carlos Guzmán A. Dirección de Sismología. INETER, Managua, Nicaragua. Tel.: (505) 249-2761 FAX: (505) 249-1082 email: If anyone know about these station you can write him directly. Thanks, Angel __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: mystery stations? From: ChrisAtUpw@....... Date: Thu, 12 Aug 2004 11:02:50 EDT In a message dated 12/08/04, sismos@.............. writes: Seeking inrormation on:- > GSV Goldstream Valley -147.937 64.9216 302.8 > GSVT Goldstream Valley - Tok -142.9821 63.3372 497 > OMCO Orchard Mesa -108.517 39.027 0 > PSDMA Soufriere -61.357 15.235 60 > PSDMB Cotton Hill -61.457 15.585 40 > PSDMZ Portsmouth -61.4563 15.577 0 >=20 > 1 Type of senor > 2 Is the station in operation > 3 Type of station > 4 Is there volcanic activity near by > 5 Is that data available >=20 > Carlos Guzm=E1n A. > Direcci=F3n de Sismolog=EDa. > INETER, Managua, Nicaragua. > Tel.: (505) 249-2761 >=20 Hi Angel / Carlos,=20 They are listed in the USGS Stations List with a query address. See=20 http://neic.usgs.gov/neis/station_book/=20 Inquiries should be directed to: Leonid Yevseyev yevseyev@........=20 =20 Regards, Chris In a message=20= dated 12/08/04, sismos@.............. writes:

Seeking inrormation on:-

GSV   Goldstream=20= Valley -147.937 64.9216 302.8
GSVT   Goldstream Valley - Tok -142.9821 63.3372 497
OMCO   Orchard Mesa -108.517 39.027 0
PSDMA  Soufriere -61.357 15.235 60
PSDMB  Cotton Hill -61.457 15.585 40
PSDMZ  Portsmouth -61.4563 15.577 0

1  Type of senor
2  Is the station in operation
3  Type of station
4  Is there volcanic activity near by
5  Is that data available

Carlos Guzm=E1n A.
Direcci=F3n de Sismolog=EDa.
INETER, Managua, Nicaragua.
Tel.: (505) 249-2761
FAX: (505) 249-1082


Hi Angel / Carlos,=20

      They are listed in the USGS Station= s List with a query address. See http://neic.usgs.gov/neis/station_book/=20
     Inquiries should be directed to: Leonid Y= evseyev yevseyev@........=20
=20
Regards,

      Chris Subject: Optical position indicator idea From: George Bush ke6pxp@....... Date: Mon, 16 Aug 2004 11:25:19 -0700 While leafing through the current issue of Electronic Design I read an ad from National Semiconductor (p. 34-35, 08/09/04 EDN) the might be of interest to amateurs who are building their own seismometers and need a way to determing the absolute position of the boom and output a signal proportional to the boom's displacement. The ad is a design idea for an application of their LMV2011 precision op amp. they are suggesting that it be used to control the output of a led and stabilize it. They are doing this by using a photo diode to look at the LED and through the op amp, feedback the signal to the LED and stabilize it's output. My thought would be to place the occulting vane on the seismometer boom in the light path and as the boom moves to obscure the light, the amp will increase the light level to make up. We should get a usable signal across the resistor that the design has in series with the LED. I do not know if this will work or if it may be too noisy or temperamental, or some other "gotchas," but I am going to try and collect the parts and play with it. You can read the application note if you are interested at: http://www.national.com/nationaledge/aug04/article.html George __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Optical position indicator idea From: ChrisAtUpw@....... Date: Mon, 16 Aug 2004 21:53:07 EDT In a message dated 16/08/04, ke6pxp@....... writes: > While leafing through the current issue of Electronic Design I read an ad > from National Semiconductor (p. 34-35, 08/09/04 EDN) the might be of interest > to amateurs who are building their own seismometers and need a way to > determine the absolute position of the boom and output a signal proportional to the > boom's displacement. The ad is a design idea for an application of their > LMV2011 precision op amp. they are suggesting that it be used to control the > output of a led and stabilise it. They are doing this by using a photo diode to > look at the LED and through the op amp, feedback the signal to the LED and > stabilise it's output. > > My thought would be to place the occulting vane on the seismometer boom in > the light path and as the boom moves to obscure the light, the amp will > increase the light level to make up. We should get a usable signal across the > resistor that the design has in series with the LED. I do not know if this will > work or if it may be too noisy or temperamental, or some other "gotchas," but I > am going to try and collect the parts and play with it. > You can read the application note if you are interested at:- > Hi George, To measure seismometer movements, you usually allow over +/-0.5mm total movement (or your seismometer becomes very difficult to set up) and you require to measure the arm position to maybe 20 nano metres for 'amateur' use. To do this you have to reduce / compensate / design for low drifts and minimum noise, both with time and with temperature - you are considering 1 part in 25,000. You need two large area photo diodes (~7sq mm - VTD34?) connected to the inverting input of two low noise opamps TLC2201? with a suitable value of feedback resistors. You then subtract the opamp outputs with a differential opamp eg INA118 and apply bandwidth filtering. This reduces the effects of temperature on the photo sensitivity and on the leakage currents. Noise considerations in photodiodes require you to use a photo current of the order of 0.5 mA, which implies a high intensity light source. The photodiodes should be fixed to a common heatsink to minimise temperature variations. It is possible to use light from one the high power, metal cased IR LEDs, but the photo output of a LED shows an exponential decrease as the temperature increases. This makes getting high stability and low noise a little bit difficult. Laser diodes tend to be very noisy. (You can buy laser diodes which have an internal photo diode to 'stabilise' the output.) An easier approach is to use a tungsten filament bulb in a feedback bridge circuit, which stabilises the hot filament resistance. You reduce the voltage on the bulb to < 0.8 x that rated. This gives an essentially infinite filament life. The dimmer filament doesn't effect the sensitivity as much as you would expect, since the sensitivity of Si photo cells increases in the near Infra Red. GaAs photocells may also be used with superbright visible orange LEDs. 'Ordinary' LEDs tend to be quite to very noisy. the superbright ones tend to be quieter. You need the dimensions of the photocells to be large compared with the wavelength of light, to minimise interference fringe effects. The minimum conduction noise in a photodiode is proportional to the square root of the photocurrent, so increasing the photocurrent will give a lower overall noise. With a significant amount of heat being shone on the photocells + optical shutter, the detector needs to be near the top of the seismometer case, maybe in a semi isolated light box, to minimise heating effects and air currents. The bulb is best mounted outside the main seismometer case, to give adequate cooling by direct contact with the housing. You can make quite good windows using Microscope slides / cover slips. There was a note on PSN some years ago which said that you couldn't use optical detectors, but this was a misunderstanding. If you try to use interference fringe methods, your resolution will be limited, commonly to a fraction of a micron. Regards, Chris Chapman In a message=20= dated 16/08/04, ke6pxp@....... writes:

While leafing through the c= urrent issue of Electronic Design I read an ad from National Semiconductor (= p. 34-35, 08/09/04 EDN) the might be of interest to amateurs who are buildin= g their own seismometers and need a way to determine the absolute position o= f the boom and output a signal proportional to the boom's displacement. The=20= ad is a design idea for an application of their LMV2011 precision op amp. th= ey are suggesting that it be used to control the output of a led and stabili= se it. They are doing this by using a photo diode to look at the LED and thr= ough the op amp, feedback the signal to the LED and stabilise it's output.=20

My thought would be to place the occulting vane on the seismometer boom=20= in the light path and as the boom moves to obscure the light, the amp will i= ncrease the light level to make up. We should get a usable signal across the= resistor that the design has in series with the LED. I do not know if this=20= will work or if it may be too noisy or temperamental, or some other "gotchas= ," but I am going to try and collect the parts and play with it.
You can read the application note if you are interested at:-
http://www.national.com/nationaledge/aug04/article.html


Hi George,

      To measure seismometer movements, y= ou usually allow over +/-0.5mm total movement (or your seismometer becomes v= ery difficult to set up) and you require to measure the arm position to mayb= e 20 nano metres for 'amateur' use. To do this you have to reduce / compensa= te / design for low drifts and minimum noise, both with time and with temper= ature - you are considering 1 part in 25,000.
      You need two large area photo diode= s (~7sq mm - VTD34?) connected to the inverting input of two low noise opamp= s TLC2201? with a suitable value of feedback resistors. You then subtract th= e opamp outputs with a differential opamp eg INA118 and apply bandwidth filt= ering. This reduces the effects of temperature on the photo sensitivity and=20= on the leakage currents. Noise considerations in photodiodes require you to=20= use a photo current of the order of 0.5 mA, which implies a high intensity l= ight source. The photodiodes should be fixed to a common heatsink to minimis= e temperature variations.
      It is possible to use light from on= e the high power, metal cased IR LEDs, but the photo output of a LED shows a= n exponential decrease as the temperature increases. This makes getting high= stability and low noise a little bit difficult. Laser diodes tend to be ver= y noisy. (You can buy laser diodes which have an internal photo diode to 'st= abilise' the output.) An easier approach is to use a tungsten filament bulb=20= in a feedback bridge circuit, which stabilises the hot filament resistance.=20= You reduce the voltage on the bulb to < 0.8 x that rated. This gives an e= ssentially infinite filament life. The dimmer filament doesn't effect the se= nsitivity as much as you would expect, since the sensitivity of Si photo cel= ls increases in the near Infra Red. GaAs photocells may also be used with su= perbright visible orange LEDs. 'Ordinary' LEDs tend to be quite to very nois= y. the superbright ones tend to be quieter.
       You need the dimensions of th= e photocells to be large compared with the wavelength of light, to minimise=20= interference fringe effects. The minimum conduction noise in a photodiode is= proportional to the square root of the photocurrent, so increasing the phot= ocurrent will give a lower overall noise. With a significant amount of heat=20= being shone on the photocells + optical shutter, the detector needs to be ne= ar the top of the seismometer case, maybe in a semi isolated light box, to m= inimise heating effects and air currents. The bulb is best mounted outside t= he main seismometer case, to give adequate cooling by direct contact with th= e housing. You can make quite good windows using Microscope slides / cover s= lips.
      There was a note on PSN some years=20= ago which said that you couldn't use optical detectors, but this was a misun= derstanding. If you try to use interference fringe methods, your resolution=20= will be limited, commonly to a fraction of a micron.    

      Regards,

      Chris Chapman Subject: RE: Optical position indicator idea From: "Coleman, Allan" allan.coleman@............ Date: Tue, 17 Aug 2004 07:39:46 -0700 Chris, =20 Have you seen the development work done by Scripps, regarding their = "experiments with an optical seismometer", based on a fringe resolver = using fiber optic interferometry? The design is beyond the capability of = most amateurs, but it is an interesting read. You can see details of = their design at: =20 http://gravity.ucsd.edu/research/OFSEIS/opt_seis.html =20 Regards, =20 Allan Coleman -----Original Message----- From: psn-l-request@.............. = [mailto:psn-l-request@................. Behalf Of ChrisAtUpw@....... Sent: Monday, August 16, 2004 6:53 PM To: psn-l@.............. Subject: Re: Optical position indicator idea <<<<<>>>>>=20 If you try to use interference fringe methods, your resolution will be = limited, commonly to a fraction of a micron. =20 Regards,=20 Chris Chapman=20
Chris,
 
Have=20 you seen the development work done by Scripps, regarding = their "experiments with an optical = seismometer", based on a fringe resolver using fiber optic=20 interferometry? The design is beyond the capability of = most=20 amateurs, but it is an interesting read. You can see details of their = design=20 at:
 
http://gra= vity.ucsd.edu/research/OFSEIS/opt_seis.html
 
Regards,
 
Allan=20 Coleman
-----Original Message-----
From: = psn-l-request@................. [mailto:psn-l-request@...............On Behalf Of=20 ChrisAtUpw@.......
Sent: Monday, August 16, 2004 6:53=20 PM
To: psn-l@..............
Subject: Re: Optical = position=20 indicator idea

<<<<<<SNIP>>>>>&g= t; 
 If you try to use interference = fringe=20 methods, your resolution will be limited, commonly to a fraction of a = micron.=20     =

      Regards,=20

      Chris=20 Chapman=20
Subject: RE: Optical position indicator idea From: Jack Ivey ivey@.......... Date: Tue, 17 Aug 2004 12:24:20 -0400 In addition to Chris' comments, I'd add that if you measure the output current of the National circuit, you will get both the desired signal plus the noise the servo is trying to take out. It might be better to use the circuit to stabilize the light output of the LED or lamp and use a separate position sensing arrangement. Jack __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Optical position indicator idea From: "Meredith Lamb" meredithlamb@............. Date: Tue, 17 Aug 2004 11:25:19 -0600 Hi all, As a simple reference followup on the optical sensing subject; one can see dialog and a circuit to Chris's Chapmans "Differential Photo Detector", on John Lahr's extensive subjects and excellent web site: http://www.jclahr.com/science/psn/chapman/photo_detect/index.html Meredith Lamb Hi George, To measure seismometer movements, you usually allow over +/-0.5mm total movement (or your seismometer becomes very difficult to set up) and you require to measure the arm position to maybe 20 nano metres for 'amateur' use. To do this you have to reduce / compensate / design for low drifts and minimum noise, both with time and with temperature - you are considering 1 part in 25,000. You need two large area photo diodes (~7sq mm - VTD34?) connected to the inverting input of two low noise opamps TLC2201? with a suitable value of feedback resistors. You then subtract the opamp outputs with a differential opamp eg INA118 and apply bandwidth filtering. This reduces the effects of temperature on the photo sensitivity and on the leakage currents. Noise considerations in photodiodes require you to use a photo current of the order of 0.5 mA, which implies a high intensity light source. The photodiodes should be fixed to a common heatsink to minimise temperature variations. It is possible to use light from one the high power, metal cased IR LEDs, but the photo output of a LED shows an exponential decrease as the temperature increases. This makes getting high stability and low noise a little bit difficult. Laser diodes tend to be very noisy. (You can buy laser diodes which have an internal photo diode to 'stabilise' the output.) An easier approach is to use a tungsten filament bulb in a feedback bridge circuit, which stabilises the hot filament resistance. You reduce the voltage on the bulb to < 0.8 x that rated. This gives an essentially infinite filament life. The dimmer filament doesn't effect the sensitivity as much as you would expect, since the sensitivity of Si photo cells increases in the near Infra Red. GaAs photocells may also be used with superbright visible orange LEDs. 'Ordinary' LEDs tend to be quite to very noisy. the superbright ones tend to be quieter. You need the dimensions of the photocells to be large compared with the wavelength of light, to minimise interference fringe effects. The minimum conduction noise in a photodiode is proportional to the square root of the photocurrent, so increasing the photocurrent will give a lower overall noise. With a significant amount of heat being shone on the photocells + optical shutter, the detector needs to be near the top of the seismometer case, maybe in a semi isolated light box, to minimise heating effects and air currents. The bulb is best mounted outside the main seismometer case, to give adequate cooling by direct contact with the housing. You can make quite good windows using Microscope slides / cover slips. There was a note on PSN some years ago which said that you couldn't use optical detectors, but this was a misunderstanding. If you try to use interference fringe methods, your resolution will be limited, commonly to a fraction of a micron. Regards, Chris Chapman
Hi all,
 
As a simple reference followup on the optical sensing subject; one can see dialog
and a circuit to Chris's Chapmans "Differential Photo Detector", on John Lahr's extensive
subjects and excellent web site:
 
 
Meredith Lamb
Hi George,

      To measure seismometer movements, you usually allow over +/-0.5mm total movement (or your seismometer becomes very difficult to set up) and you require to measure the arm position to maybe 20 nano metres for 'amateur' use. To do this you have to reduce / compensate / design for low drifts and minimum noise, both with time and with temperature - you are considering 1 part in 25,000.
      You need two large area photo diodes (~7sq mm - VTD34?) connected to the inverting input of two low noise opamps TLC2201? with a suitable value of feedback resistors. You then subtract the opamp outputs with a differential opamp eg INA118 and apply bandwidth filtering. This reduces the effects of temperature on the photo sensitivity and on the leakage currents. Noise considerations in photodiodes require you to use a photo current of the order of 0.5 mA, which implies a high intensity light source. The photodiodes should be fixed to a common heatsink to minimise temperature variations.
      It is possible to use light from one the high power, metal cased IR LEDs, but the photo output of a LED shows an exponential decrease as the temperature increases. This makes getting high stability and low noise a little bit difficult. Laser diodes tend to be very noisy. (You can buy laser diodes which have an internal photo diode to 'stabilise' the output.) An easier approach is to use a tungsten filament bulb in a feedback bridge circuit, which stabilises the hot filament resistance. You reduce the voltage on the bulb to < 0.8 x that rated. This gives an essentially infinite filament life. The dimmer filament doesn't effect the sensitivity as much as you would expect, since the sensitivity of Si photo cells increases in the near Infra Red. GaAs photocells may also be used with superbright visible orange LEDs. 'Ordinary' LEDs tend to be quite to very noisy. the superbright ones tend to be quieter.
       You need the dimensions of the photocells to be large compared with the wavelength of light, to minimise interference fringe effects. The minimum conduction noise in a photodiode is proportional to the square root of the photocurrent, so increasing the photocurrent will give a lower overall noise. With a significant amount of heat being shone on the photocells + optical shutter, the detector needs to be near the top of the seismometer case, maybe in a semi isolated light box, to minimise heating effects and air currents. The bulb is best mounted outside the main seismometer case, to give adequate cooling by direct contact with the housing. You can make quite good windows using Microscope slides / cover slips.
      There was a note on PSN some years ago which said that you coul dn't use optical detectors, but this was a misunderstanding. If you try to use interference fringe methods, your resolution will be limited, commonly to a fraction of a micron.    

      Regards,

      Chris Chapman
Subject: ebay auction From: BOB BARNS royb1@........... Date: Fri, 20 Aug 2004 10:04:28 -0400 Hi gang, Velocity Seismoprobe Item number: 3834584179 ends Aug 25 Starting price is $10 Bob __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: PSN map and list clean up From: Dave Nelson davenn@............... Date: Sat, 21 Aug 2004 23:09:15 +1000  Hi guys,
               after some 5 years of the PSN map and database being online
I have decided its time to do a cleanout   ie. some spring cleaning   :)
  I'm sure  there are people listed in the database that are no longer active
either in seismology or on the email listserver

 The best way, I think, to sort this out is for everyone to email me
( DIRECTLY)    not via the list server   we dont wanna clutter it up
to confirm their presence within the PSN group

 Anyone not heard from within 1 month of this email will be deemed no longer
active and will be noted as ready from removal within the following month
1 month should be long enuf for people to respond   unless they are on excessively
long holidays ( lucky people  :)    )

you may want to take this opportunity to check ur listing details and make sure they are correct and let me know what, if anything, needs changing

looking forward to hearing from you all

cheers
Dave





Subject: Re: PSN map and list clean up From: "Thomas Dick" dickthomas01@............. Date: Sat, 21 Aug 2004 08:42:07 -0500 Dave Nelson The best way, I think, to sort this out is for everyone to email me ( DIRECTLY) Anyone not heard from within 1 month of this email will be deemed no longer I want to continue hearing from you -- don't have email address for you -- am close to bringing up eqwuipment here in southern Indiana __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: PSN map and list clean up From: Karl Cunningham karlc@.......... Date: Sat, 21 Aug 2004 07:45:02 -0700 Hi Dave -- Great to hear from you. I've checked my listing and all is ok except the email address. Which brings up another point... Being as the list is on a publicly-accessible web page, we probably should list people's email addresses disguised in some way to discourage spammers. I've heard spammers are wise to stuff like "joe at domain dot com" so we probably should use something a bit more creative than that. In any case, please change my email address on the list to seismo8@........... I have my own domain and mail server, so I can use whatever email address I like. Using seismo8 will let me see when the spammers have figured out the disguise. Thanks for your work in this. Later. Karl --On Saturday, August 21, 2004 23:09 +1000 Dave Nelson wrote: > Hi guys, > after some 5 years of the PSN map and database being online > I have decided its time to do a cleanout ie. some spring cleaning :) > I'm sure there are people listed in the database that are no longer > active either in seismology or on the email listserver > > The best way, I think, to sort this out is for everyone to email me > ( DIRECTLY) not via the list server we dont wanna clutter it up > to confirm their presence within the PSN group > > Anyone not heard from within 1 month of this email will be deemed no > longer active and will be noted as ready from removal within the > following month 1 month should be long enuf for people to respond > unless they are on excessively long holidays ( lucky people :) ) > > you may want to take this opportunity to check ur listing details and > make sure they are correct and let me know what, if anything, needs > changing > > looking forward to hearing from you all > > cheers > Dave > > > > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: PSN map and list clean up From: Karl Cunningham karlc@.......... Date: Sat, 21 Aug 2004 07:51:12 -0700 Sorry for the post to the list, rather than directly to Dave. I REALLY do know better. Karl __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: PSN map and list clean up From: "Tom Frey" seismo2@........... Date: Sat, 21 Aug 2004 09:28:32 -0700 Greetings Dave Please change my email address from tfreyis@......... to = tfreyis@............ thanx tom
Greetings Dave
 
Please change my email address from tfreyis@......... to tfreyis@............
=
thanx
tom
Subject: RE: PSN map and list clean up From: "Jan D. Marshall" jandmarshall@............ Date: Sat, 21 Aug 2004 11:05:27 -0600 wonderful idea Dave -- what is your DIRECT email address??? Please note new email address Jan Marshall janmarshall@....... http://myweb.cableone.net/jandmarshall/ Nampa, ID -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@................. Behalf Of Dave Nelson Sent: Saturday, August 21, 2004 7:09 AM To: psn-l@.............. Subject: PSN map and list clean up Hi guys, after some 5 years of the PSN map and database being online I have decided its time to do a cleanout ie. some spring cleaning :) I'm sure there are people listed in the database that are no longer active either in seismology or on the email listserver The best way, I think, to sort this out is for everyone to email me ( DIRECTLY) not via the list server we dont wanna clutter it up to confirm their presence within the PSN group Anyone not heard from within 1 month of this email will be deemed no longer active and will be noted as ready from removal within the following month 1 month should be long enuf for people to respond unless they are on excessively long holidays ( lucky people :) ) you may want to take this opportunity to check ur listing details and make sure they are correct and let me know what, if anything, needs changing looking forward to hearing from you all cheers Dave
wonderful idea Dave -- what is your DIRECT email=20 address???
 

Please note new email=20 address

Jan Marshall
janmarshall@.......
http://myweb.cableone.net= /jandmarshall/
Nampa, ID

-----Original Message-----
From: = psn-l-request@................. [mailto:psn-l-request@...............On Behalf Of Dave=20 Nelson
Sent: Saturday, August 21, 2004 7:09 AM
To: = psn-l@..............
Subject: PSN map and list clean=20 up

 Hi=20 = guys,
          &nbs= p;   =20 after some 5 years of the PSN map and database being online
I have = decided=20 its time to do a cleanout   ie. some spring = cleaning  =20 :)
  I'm sure  there are people listed in the database = that are=20 no longer active
either in seismology or on the email=20 listserver

 The best way, I think, to sort this out is for = everyone to email me
( DIRECTLY)    not via the = list=20 server   we dont wanna clutter it up
to confirm their = presence within the PSN group

 Anyone not heard from = within 1=20 month of this email will be deemed no longer
active and will be = noted as=20 ready from removal within the following month
1 month should be = long enuf=20 for people to respond   unless they are on = excessively
long=20 holidays ( lucky people  :)    )

you may = want to=20 take this opportunity to check ur listing details and make sure they = are=20 correct and let me know what, if anything, needs = changing

looking=20 forward to hearing from you all

cheers
Dave=20





Subject: RE: PSN map and list clean up From: apsn@........... Date: Sat, 21 Aug 2004 10:35:33 -0800 (AKDT) Guys, Dave's direct email address was in the header.... :) Bob Hammond http://apsn.awcable.com > wonderful idea Dave -- what is your DIRECT email address??? > > Please note new email address > > Jan Marshall > janmarshall@....... > http://myweb.cableone.net/jandmarshall/ > Nampa, ID > > -----Original Message----- > From: psn-l-request@.............. > [mailto:psn-l-request@................. > Behalf Of Dave Nelson > Sent: Saturday, August 21, 2004 7:09 AM > To: psn-l@.............. > Subject: PSN map and list clean up > > > Hi guys, > after some 5 years of the PSN map and database being > online > I have decided its time to do a cleanout ie. some spring cleaning > :) > I'm sure there are people listed in the database that are no longer > active > either in seismology or on the email listserver > > The best way, I think, to sort this out is for everyone to email me > ( DIRECTLY) not via the list server we dont wanna clutter it up > to confirm their presence within the PSN group > > Anyone not heard from within 1 month of this email will be deemed no > longer > active and will be noted as ready from removal within the following > month 1 month should be long enuf for people to respond unless they > are on > excessively > long holidays ( lucky people :) ) > > you may want to take this opportunity to check ur listing details and > make > sure they are correct and let me know what, if anything, needs changing > > looking forward to hearing from you all > > cheers > Dave __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: PSN map and list clean up From: Dave Nelson davenn@............... Date: Sun, 22 Aug 2004 12:03:05 +1000 At 07:45 AM 21/08/2004 -0700, you wrote: >Hi Dave -- >Great to hear from you. >.......In any case, please change my email address on the list to >seismo8@........... I have my own domain and mail server, so I can use ..... >Thanks for your work in this. >Later. >Karl Hi Karl .... trust all is well with u and ur better half :) will get back to Calif again one day for a holiday. ok the email addy have been updated Im still living on the 3rd floor of an apartment block here so impossible to run a seismic station hopefully one day will get a standard groundlevel home to rent so I can get a station up and running again cheers and take care Dave Subject: grrrr and other database comments From: Dave Nelson davenn@............... Date: Sun, 22 Aug 2004 12:12:39 +1000 darn it now I did it sorry all responded to Karl's posted msg not prv email while I am writing this ..... it has become apparent from the email respondants that there is a growing number of you that are on the email list server but are not on the PSN maps or in the database of seismic stations please go to http://www.seismicnet.com/dave/map.htm and check out the interactive (clickable) maps and associated database and see if you would like to be added .... It is possible that you didnt even know they existed. I have already started responding to some of you directly cheers Dave PS for those of you who didnt know my email addy just look in the header of this mail thanks to the person who also pointed that out :)) Subject: Re: PSN map and list clean up From: Dave Nelson davenn@............... Date: Sun, 22 Aug 2004 12:39:59 +1000 At 09:28 AM 21/08/2004 -0700, you wrote:
Greetings Dave
Please change my email address from tfreyis@......... to tfreyis@............
thanx
tom


 Thanks Tom          all done

Dave
Subject: a change in the email listing in the station databases From: Dave Nelson davenn@............... Date: Sun, 22 Aug 2004 16:52:43 +1000 hi again guys, after comments from Karl C, Larry C and Bob H about the email spamming problems on the internet these days, I have decided to make a change which although makes emailing someone on the list a little more awkward hopefully it will make listing your email addy's somewhat safer. this text (below) also appears near the top of of the 2 database pages..... http://www.seismicnet.com/dave/people.htm and http://www.seismicnet.com/dave/people1.htm In an effort to stop email addy harvesting for spamming, I have removed the active email addy. Instead there is just a text version along with extra text in the addy that needs to be removed after the addy is copied and pasted into your email prog. remove the word ... antispam ... from the addy before sending. my email will remain a clickable addy, my ISP has pretty good antispam software in use cheers all Dave N Subject: RE: grrrr and other database comments From: "richard a phillips" raphillips5@............. Date: Sun, 22 Aug 2004 22:36:35 -0500 Dave, Please keep me on the mailing list. Thanks, Rick Phillips __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: PSN map and list clean up From: "Edward M. Brown" ebrown@.......... Date: Mon, 23 Aug 2004 12:41:53 -0600 Hello Dave, Saturday, August 21, 2004, 7:09:15 AM, you wrote: >  Hi guys, >               after some 5 years of the PSN map and database being online > I have decided its time to do a cleanout   ie. some springcleaning   :) >   I'm sure  there are people listed in the database that are nolonger active > either in seismology or on the email listserver >  The best way, I think, to sort this out is for everyone to emailme > ( DIRECTLY)    not via the list server   wedont wanna clutter it up > to confirm their presence within the PSN group >  Anyone not heard from within 1 month of this email will be deemedno longer > active and will be noted as ready from removal within the followingmonth > 1 month should be long enuf for people to respond   unless theyare on excessively > long holidays ( lucky people  :)    ) > you may want to take this opportunity to check ur listing details > andmake sure they are correct and let me know what, if anything, > needschanging > looking forward to hearing from you all > cheers > Dave Dave, I'm still here. -- Best regards, Ed mailto:ebrown@.......... __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: PSN map and list clean up From: Mauro Mariotti mariotti@......... Date: Tue, 24 Aug 2004 15:12:31 +0200 Hi Dave, i confirm my station with 3 axis 1 vertical 1.2 seconds 2 horizontal 5 seconds 16 bit a/d Perugia - Italy regards mauro At 15:09 21/08/2004, you wrote: > Hi guys, > after some 5 years of the PSN map and database being online >I have decided its time to do a cleanout ie. some spring cleaning :) > I'm sure there are people listed in the database that are no longer active >either in seismology or on the email listserver > > The best way, I think, to sort this out is for everyone to email me >( DIRECTLY) not via the list server we dont wanna clutter it up >to confirm their presence within the PSN group > > Anyone not heard from within 1 month of this email will be deemed no longer >active and will be noted as ready from removal within the following month >1 month should be long enuf for people to respond unless they are on >excessively >long holidays ( lucky people :) ) > >you may want to take this opportunity to check ur listing details and make >sure they are correct and let me know what, if anything, needs changing > >looking forward to hearing from you all > >cheers >Dave > > > > __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Digest from 08/23/2004 00:01:03 From: wlshedri@................... Date: Tue, 24 Aug 2004 08:24:20 -0700 I wish to remain on the list Warren S |---------+-----------------------------------> | | psn-l-digest-request@web| | | tronics.com | | | | | | 08/24/2004 12:00 AM | | | Please respond to psn-l | | | | |---------+-----------------------------------> >--------------------------------------------------------------------= ----------------------------------------------------------| | = | | To: psn-l-digest@.............. = | | cc: = | | Subject: Digest from 08/23/2004 00:01:03 = | >--------------------------------------------------------------------= ----------------------------------------------------------| ..------ ------ ------ ------ ------ ------ ------ ------ ------ ------.= | Message 1 |= '------ ------ ------ ------ ------ ------ ------ ------ ------ ------'= Subject: Re: PSN map and list clean up From: "Edward M. Brown" Date: Mon, 23 Aug 2004 12:41:53 -0600 Hello Dave, Saturday, August 21, 2004, 7:09:15 AM, you wrote: > =A0Hi guys, > =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0=A0after some 5 years of the P= SN map and database being online > I have decided its time to do a cleanout=A0=A0 ie. some springcleanin= g=A0=A0 :) > =A0 I'm sure=A0 there are people listed in the database that are nolo= nger active > either in seismology or on the email listserver > =A0The best way, I think, to sort this out is for everyone to emailme= > ( DIRECTLY)=A0=A0=A0 not via the list server=A0=A0 wedont wanna clutt= er it up > to confirm their presence within the PSN group > =A0Anyone not heard from within 1 month of this email will be deemedn= o longer > active and will be noted as ready from removal within the followingmo= nth > 1 month should be long enuf for people to respond=A0=A0 unless theyar= e on excessively > long holidays ( lucky people=A0 :)=A0=A0=A0 ) > you may want to take this opportunity to check ur listing details > andmake sure they are correct and let me know what, if anything, > needschanging > looking forward to hearing from you all > cheers > Dave -- Best regards, Ed mailto:ebrown@.......... __________________________________________________________ Public Seismic Network Mailing List (PSN-L) To leave this list email PSN-L-DIGEST-REQUEST@.............. with the body of the message (first line only): unsubscribe See http://www.seismicnet.com/maillist.html for more information. = __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: Digest from 08/23/2004 00:01:03 From: Dave Nelson davenn@............... Date: Wed, 25 Aug 2004 06:20:32 +1000 At 08:24 AM 24/08/2004 -0700, you wrote: >I wish to remain on the list >Warren S Hi Warren, you are on the email list but you are not on the PSN Station map and database..... do you have a seismic station? if so would you like to get onto the database ?? this call I put out was for PSN members that have seismic stations listed in the database and on the maps at http://www.seismicnet.com/dave/map.htm and the areas of the world linked to that page (its an interactive map(clickable)) you will see a list of the data I collect about each seismic station to put in the database If you would like to be included please respond with the info cheers Dave Subject: ebay auction From: BOB BARNS royb1@........... Date: Wed, 25 Aug 2004 13:39:56 -0400 Hi gang, Seismograph Geometrics Nimbus Instruments Mod. ES-125 Item number: 2265330303 ends Aug 31 price now $50. Bob *** Reunite Gondwanaland! *** __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: WQFilter demo From: "rem11560@............ rem11560@netzero.com Date: Thu, 26 Aug 2004 04:57:51 GMT Hi all, On seismicnet's "New PSN Earthquake Data Files" page, you will find listed: 040821.080000.jcc1x.psn * M4.3 1,609 km from Pearland,TX (raw and WQFILTER'd) : GULF OF CALIFORNIA (GIF Image) I prepared and submitted this file using the data from: 040821.075808.jcc1.psn M 4.3 ,1,609 km from Pearland,TX. USA (single spring) (raw data) GULF OF CALIFORNIA (GIF Image) It is an excellent demonstration of the ability of the period extending filter in WQFilter.exe to resurrect long period data from a short period sensor. To make comparison easier, I forced channel jcc1 to have the same full scale display as channel jcc1x by patching in 18760 as the first data point. If you download this file, take a look at the spectra of the two channels (exclude the first few seconds of data), as well as an expanded scale inspection of the waveforms. Look at "Data Operations" to see what was done to make jcc1x. Regards, Bob McClure ________________________________________________________________ The best thing to hit the Internet in years - NetZero HiSpeed! Surf the Web up to FIVE TIMES FASTER! Only $14.95/ month -visit www.netzero.com to sign up today! __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: grrrr and other database comments From: Dave Nelson davenn@............... Date: Fri, 27 Aug 2004 18:40:47 +1000 At 10:36 PM 22/08/2004 -0500, you wrote: >Dave, >Please keep me on the mailing list. >Thanks, >Rick Phillips Hi Rick, you are on the email list but you are not on the PSN Station map and database..... do you have a seismic station? if so would you like to get onto the database ?? this call I put out was for PSN members that have seismic stations listed in the database and on the maps at http://www.seismicnet.com/dave/map.htm and the areas of the world linked to that page (its an interactive map(clickable)) you will see a list of the data I collect about each seismic station to put in the database If you would like to be included please respond with the info cheers Dave Subject: My thoughts on seismic data filtering From: "rem11560@............ rem11560@netzero.com Date: Sat, 28 Aug 2004 19:58:51 GMT Hi all, I am a retired defense R&D engineer, with experience in many things, such as electro-optics, lidar, ring laser rate sensors, inertial navigation, electronic surveillance, computer programming, and digital data acquisition and processing. I have no professional experience in seismology or seismometry. For the past three years, I have pursued the hobby of amateur seismography, building sensors of my own design, and becoming somewhat adept at writing Visual Basic applications for use in seismometry. I did not even know of the existence of the Public Seismic Network until John Lahr urged me to participate, noting that the group was always willing to help new members. I got started with Dataq A/D's, not even knowing that there were other options, such as WinSDR and WinQuake to build a system around, so I had to code most of my logging, data processing, and display software. When I progressed to the point where I wanted to submit event files to Seismicnet, I had to write my own application to convert Dataq files, to PSN Type 4 format. So, with the above background and caveats, I would like to offer the following discourse on the subject of filtering seismic signals. I hope it stimulates some discussion. I like to read the letters from the PSN List. ~~~~~~~~~~~~ MY THOUGHTS ON SEISMIC DATA FILTERING. On most seismic events, it is necessary to filter the raw data in order to suppress cultural noise and microseisms to get a better view of the ground motions of the event. First off, the sensor itself filters the data, and the amplifier filters the sensor output. The digitization process can also filter (and distort) the data. We can never truly sense ground motion, but we can hope to reproduce accurately enough the data of interest. Sensors of the force feedback type are best for high fidelity detection of ground motion. Most amateurs are limited to the use of open loop pendulum types, such as the horizontal Lehman sensor and vertical sensors of the spring supported pendulum type. Open loop sensors can only accurately reproduce signals appreciably higher than the natural resonant frequency of the pendulum. A signal at the resonant frequency of the pendulum is shifted 90 degrees lagging in phase, and its amplitude is proportional to the Q of the system. Q is inversely proportional to the damping factor, D. The relationship is Q = 0.5/D. Critical damping occurs when D=1 or Q=0.5. Usual practice is to adjust damping to a value of about 0.7, just low enough to sense a little overshoot on the return of a displaced pendulum to equilibrium. If you use more damping, you have little idea of how much it is, and if you use less damping, you may get ringing on seismic signals. At frequencies below resonance, the response falls off rapidly at a rate of 12 decibels per octave, and the phase shift heads toward 180 degrees lagging. One can infer from the above that one should strive for a pendulum period longer than the longest period one wishes to reproduce. However, the difficulty of achieving this goal goes up as the square of the period. Horizontal sensors cannot distinguish the difference between horizontal ground acceleration and ground tilt, and the response to tilt goes up as the square of the period. Most amateurs have do not site really stable in tilt. The same can be said for temperature stability. Temperature fluctuations can cause the sensor to change its alignment, producing the same problems as ground tilt changes. All this said, we amateurs just have to do the best we can with what we have. After the sensor comes the amplifier, which must also attenuate high frequency signal components to avoid aliasing at the subsequent sampling and digitization steps. Less low pass filtering is needed the higher the sampling rate. It is best to sample at a high rate, and then sample average n data points taken at the high rate to get a final sample rate 1/n times the input sample rate. My Dataq acquisition system does that automatically for me. Its A/D samples at 240 samples per second overall. If I record three channels, each is being sampled at a rate of 80 samples per second. I usually set my recorded rate at 5 samples per second per channel, so the Dataq recorder averages 16 data samples for each data point recorded. This process largely avoids any aliasing, effectively suppresses high frequency noise, and gives me 14 bit resolution out my 12 bit A/D. Once we have logged data, we still must usually digitally filter it to suppress unwanted frequency components, both low frequencies and high frequencies. However, filtering done inappropriately can really mess up the waveform of the signal we want to preserve. WinQuake is a marvelous program, grateful thanks to Larry Cochrane, and we would be in the Dark Ages without it. However, it offers so many choices on filtering that the naive user has ample opportunity to do bad things. I do not believe in ever using more than 4 poles in the filters, for example. The more poles you use, the sharper the cutoff, the more the signal is time delayed and distorted, and more ringing may occur. I also do not prefer the Butterworth filter, which is the only IIR choice offered. I have coded for my own use a selection of low-pass filter types: (1), 2-pole simple poles; (2), 4-pole simple poles; (3), 4-pole Bessel; and (4), 4-pole Butterworth. My filters are not causal (i.e., operating only on present and past data, as analog filters do), but operate on past, present, and future data to yield the present filtered data point. What I do to achieve this is to filter the data series forward in time in the usual manner, and then apply the filter to that result again, but backward in time. This results in output data that is undistorted in time and phase. To use a photographic analogy, it softens the noise in a grainy picture by defocusing it rather than smearing it. Most often, I use a simple one pole R-C filter run forward and backward to yield the 2-pole zero lag filter. Its response is 6 dB down at the corner frequency, and falls at the rate of 12 dB per octave for period shorter than the corner, a fairly soft roll-off compared to the Butterworth in WinQuake. It suppresses high frequencies, but not so much that you don't know they are there. It does not ring at all. WinQuake also features FFT filtering, which is also non-causal and yields zero lag and no phase distortion. I have tested its spectral response, and find that even the 2 pole low-pass option has a sharper cutoff than my 2 pole RC filter. If you use FFT filtering, I recommend no more than 2 to 4 poles. I have also developed a special filter for extending the useful bandwidth of an open loop sensor to lower frequencies. It is essentially a mathematically correct "bass boost" amplifier that compensates for the fall off of response of the sensor to frequencies below the natural period, and can even correct for the gain error caused by damping. To get the correct output, the sensor's natural period must be accurately known. The damping factor must also be known, but that is not so critical. My vertical sensor has a period of 5.0 seconds. I routinely apply this filter to its data, to emulate the output of a 16-second sensor. My horizontal sensors are adjusted to 14 and 8 seconds, respectively, and I routinely extend their period to 24 seconds. I get heliplots that closely resemble those displayed at the nearby LDEO Palisades web site, which uses expensive Guralp force feedback sensors, but of course I show reduced amplitude on very long period waves, and a lot more cultural noise. I use DC coupled amplifiers in order not to attenuate further the low amplitude low frequency signal components. Along with the longer period performance comes greater sensitivity to tilt from moving around my site and from wind. I can't get away from that. What is very bad and troublesome at times is that any spurious spikes in the data show up in the filtered output as large transients, like someone tapped a long period pendulum. As I have mentioned to the list before, I have written a utility program called WQFilter which can be used to apply all my filters to WinQuake event files. should you want to experiment, you can get the latest version from me. Since it is very difficult to build open loop vertical sensors having more than a few seconds natural period, my period extending filter is practically a must for amateur vertical sensors. I would encourage amateurs to acquire or build vertical sensors. They are much better than horizontal sensors for detecting P waves. They do not respond to ground tilt, so their signals are ideal for digital period extension filtering. ~~~~~~~~~~~~~~ If anyone wants to reply, I beg you not to attach this original to your message. It is overly long, so replies with the original attached will just fill up mine and others mailboxes. The original can always be seen in the archives. Thank you. Regards, Bob McClure bobhelenmcclureantispamataoldotcom rem11560antispamatnetzerodotcom http://www.jclahr.com/science/psn/mcclure/ ________________________________________________________________ The best thing to hit the Internet in years - NetZero HiSpeed! Surf the Web up to FIVE TIMES FASTER! Only $14.95/ month -visit www.netzero.com to sign up today! __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: My thoughts on seismic data filtering From: "Steve Hammond" shammon1@............. Date: Sat, 28 Aug 2004 13:10:23 -0700 Nice write-up Bob, Thanks-- Steve Hammond -----Original Message----- From: psn-l-request@.............. [mailto:psn-l-request@................. Behalf Of rem11560@........... Sent: Saturday, August 28, 2004 12:59 PM To: psn-l@.............. Subject: My thoughts on seismic data filtering Hi all, I am a retired defense R&D engineer, with experience in many things, such as electro-optics, lidar, ring laser rate sensors, inertial navigation, electronic surveillance, computer programming, and digital data acquisition and processing. I have no professional experience in seismology or seismometry. For the past three years, I have pursued the hobby of amateur seismography, building sensors of my own design, and becoming somewhat adept at writing Visual Basic applications for use in seismometry. I did not even know of the existence of the Public Seismic Network until John Lahr urged me to participate, noting that the group was always willing to help new members. I got started with Dataq A/D's, not even knowing that there were other options, such as WinSDR and WinQuake to build a system around, so I had to code most of my logging, data processing, and display software. When I progressed to the point where I wanted to submit event files to Seismicnet, I had to write my own application to convert Dataq files, to PSN Type 4 format. So, with the above background and caveats, I would like to offer the following discourse on the subject of filtering seismic signals. I hope it stimulates some discussion. I like to read the letters from the PSN List. ~~~~~~~~~~~~ MY THOUGHTS ON SEISMIC DATA FILTERING. On most seismic events, it is necessary to filter the raw data in order to suppress cultural noise and microseisms to get a better view of the ground motions of the event. First off, the sensor itself filters the data, and the amplifier filters the sensor output. The digitization process can also filter (and distort) the data. We can never truly sense ground motion, but we can hope to reproduce accurately enough the data of interest. Sensors of the force feedback type are best for high fidelity detection of ground motion. Most amateurs are limited to the use of open loop pendulum types, such as the horizontal Lehman sensor and vertical sensors of the spring supported pendulum type. Open loop sensors can only accurately reproduce signals appreciably higher than the natural resonant frequency of the pendulum. A signal at the resonant frequency of the pendulum is shifted 90 degrees lagging in phase, and its amplitude is proportional to the Q of the system. Q is inversely proportional to the damping factor, D. The relationship is Q = 0.5/D. Critical damping occurs when D=1 or Q=0.5. Usual practice is to adjust damping to a value of about 0.7, just low enough to sense a little overshoot on the return of a displaced pendulum to equilibrium. If you use more damping, you have little idea of how much it is, and if you use less damping, you may get ringing on seismic signals. At frequencies below resonance, the response falls off rapidly at a rate of 12 decibels per octave, and the phase shift heads toward 180 degrees lagging. One can infer from the above that one should strive for a pendulum period longer than the longest period one wishes to reproduce. However, the difficulty of achieving this goal goes up as the square of the period. Horizontal sensors cannot distinguish the difference between horizontal ground acceleration and ground tilt, and the response to tilt goes up as the square of the period. Most amateurs have do not site really stable in tilt. The same can be said for temperature stability. Temperature fluctuations can cause the sensor to change its alignment, producing the same problems as ground tilt changes. All this said, we amateurs just have to do the best we can with what we have. After the sensor comes the amplifier, which must also attenuate high frequency signal components to avoid aliasing at the subsequent sampling and digitization steps. Less low pass filtering is needed the higher the sampling rate. It is best to sample at a high rate, and then sample average n data points taken at the high rate to get a final sample rate 1/n times the input sample rate. My Dataq acquisition system does that automatically for me. Its A/D samples at 240 samples per second overall. If I record three channels, each is being sampled at a rate of 80 samples per second. I usually set my recorded rate at 5 samples per second per channel, so the Dataq recorder averages 16 data samples for each data point recorded. This process largely avoids any aliasing, effectively suppresses high frequency noise, and gives me 14 bit resolution out my 12 bit A/D. Once we have logged data, we still must usually digitally filter it to suppress unwanted frequency components, both low frequencies and high frequencies. However, filtering done inappropriately can really mess up the waveform of the signal we want to preserve. WinQuake is a marvelous program, grateful thanks to Larry Cochrane, and we would be in the Dark Ages without it. However, it offers so many choices on filtering that the naive user has ample opportunity to do bad things. I do not believe in ever using more than 4 poles in the filters, for example. The more poles you use, the sharper the cutoff, the more the signal is time delayed and distorted, and more ringing may occur. I also do not prefer the Butterworth filter, which is the only IIR choice offered. I have coded for my own use a selection of low-pass filter types: (1), 2-pole simple poles; (2), 4-pole simple poles; (3), 4-pole Bessel; and (4), 4-pole Butterworth. My filters are not causal (i.e., operating only on present and past data, as analog filters do), but operate on past, present, and future data to yield the present filtered data point. What I do to achieve this is to filter the data series forward in time in the usual manner, and then apply the filter to that result again, but backward in time. This results in output data that is undistorted in time and phase. To use a photographic analogy, it softens the noise in a grainy picture by defocusing it rather than smearing it. Most often, I use a simple one pole R-C filter run forward and backward to yield the 2-pole zero lag filter. Its response is 6 dB down at the corner frequency, and falls at the rate of 12 dB per octave for period shorter than the corner, a fairly soft roll-off compared to the Butterworth in WinQuake. It suppresses high frequencies, but not so much that you don't know they are there. It does not ring at all. WinQuake also features FFT filtering, which is also non-causal and yields zero lag and no phase distortion. I have tested its spectral response, and find that even the 2 pole low-pass option has a sharper cutoff than my 2 pole RC filter. If you use FFT filtering, I recommend no more than 2 to 4 poles. I have also developed a special filter for extending the useful bandwidth of an open loop sensor to lower frequencies. It is essentially a mathematically correct "bass boost" amplifier that compensates for the fall off of response of the sensor to frequencies below the natural period, and can even correct for the gain error caused by damping. To get the correct output, the sensor's natural period must be accurately known. The damping factor must also be known, but that is not so critical. My vertical sensor has a period of 5.0 seconds. I routinely apply this filter to its data, to emulate the output of a 16-second sensor. My horizontal sensors are adjusted to 14 and 8 seconds, respectively, and I routinely extend their period to 24 seconds. I get heliplots that closely resemble those displayed at the nearby LDEO Palisades web site, which uses expensive Guralp force feedback sensors, but of course I show reduced amplitude on very long period waves, and a lot more cultural noise. I use DC coupled amplifiers in order not to attenuate further the low amplitude low frequency signal components. Along with the longer period performance comes greater sensitivity to tilt from moving around my site and from wind. I can't get away from that. What is very bad and troublesome at times is that any spurious spikes in the data show up in the filtered output as large transients, like someone tapped a long period pendulum. As I have mentioned to the list before, I have written a utility program called WQFilter which can be used to apply all my filters to WinQuake event files. should you want to experiment, you can get the latest version from me. Since it is very difficult to build open loop vertical sensors having more than a few seconds natural period, my period extending filter is practically a must for amateur vertical sensors. I would encourage amateurs to acquire or build vertical sensors. They are much better than horizontal sensors for detecting P waves. They do not respond to ground tilt, so their signals are ideal for digital period extension filtering. ~~~~~~~~~~~~~~ If anyone wants to reply, I beg you not to attach this original to your message. It is overly long, so replies with the original attached will just fill up mine and others mailboxes. The original can always be seen in the archives. Thank you. Regards, Bob McClure bobhelenmcclureantispamataoldotcom rem11560antispamatnetzerodotcom http://www.jclahr.com/science/psn/mcclure/ ________________________________________________________________ The best thing to hit the Internet in years - NetZero HiSpeed! Surf the Web up to FIVE TIMES FASTER! Only $14.95/ month -visit www.netzero.com to sign up today! __________________________________________________________ Public Seismic Network Mailing List (PSN-L) __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: My thoughts on seismic data filtering From: ChrisAtUpw@....... Date: Sun, 29 Aug 2004 06:28:42 -0400 28/8/2004 From:"rem11560@..........." Since it is very difficult to build open loop vertical sensors having more than a few seconds natural period. Hi Bob, This is only true if you use short arm Lehmans and a point on a plane bottom hinge. If you make the arm 1 m long and use foil or wire, crossed cylinder, or ball on flat suspensions, you should be able to get 20 to 30 seconds period with few if any problems. Having the 1 m arm reduces the admittedly rather large sensitivity to tilt. Getting reliable operation out of a 1 ft arm at 30 seconds requires very high quality hinges and precision slow motion levelling screws, but you have a high tilt sensitivity built in. Crossed cylinder suspensions may be made from the shanks of solid tungsten carbide 0.125" drills. The finish seems to be good on the ones that I have tried, but you can lap / polish with diamond paste and a copper tube. Ball on a flat systems can be made using stainless steel ball bearings resting on a ~0.3" sided tungsten carbide flat topped lathe ''cutting tool insert''. Again, I have found the top finish adequate, but you can polish the surface to a mirror finish without too much effort. You do need these really hard corrosion resistant materials, but they are not too expensive and should be readily available from engineering suppliers. Regards, Chris Chapman __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: My thoughts on seismic data filtering From: "rem11560@............ rem11560@netzero.com Date: Mon, 30 Aug 2004 01:39:45 GMT Hi Chris, I think you misunderstood what I said, which was "Since it is very difficult to build open loop vertical sensors having more than a few seconds natural period...". I was not including horizontal sensors in this statement, only vertical ones. Cheers, Bob ________________________________________________________________ The best thing to hit the Internet in years - NetZero HiSpeed! Surf the Web up to FIVE TIMES FASTER! Only $14.95/ month -visit www.netzero.com to sign up today! __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: ebay auction From: BOB BARNS royb1@........... Date: Thu, 09 Sep 2004 10:53:00 -0400 Hi gang, Triaxial indicating solid state Seismograph Seismometer 1'st on eBay! Self contained alarming seismometer Item number: 6117800332 auction ends 8/18 Additonl info on this device by someone on the psn list would be helpful. Bob __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: ebay auction From: BOB BARNS royb1@........... Date: Mon, 13 Sep 2004 10:09:40 -0400 Hi gang, Lehman seismograph sensor Item number: 5520337743 ends Sept 19 Bob __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: ebay auction !!! From: BOB BARNS royb1@........... Date: Tue, 14 Sep 2004 11:38:14 -0400 Hi gang, This looks like a highly desireable item! Geotech SL-210 Vertical Long Period Seismometer *NR* Item number: 6118994421 ends Sept. 20 Bob __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: GT+ Encore GPS Test From: "Rex Klopfenstein, Jr." rklopfen@......... Date: Sun, 19 Sep 2004 21:23:03 -0400 Could someone point me to a software package that I could use to verify = the operation of my GT+ Encore GPS with TARP Interface board? Its been = about 4 years since I have been active on this list. Rex Klopfenstein Bowling Green, OH
Could someone point me to a software = package that I=20 could use to verify the operation of my GT+ Encore GPS with TARP = Interface=20 board?  Its been about 4 years since I have been active on this=20 list.

Rex Klopfenstein
Bowling Green, OH
Subject: Re: GT+ Encore GPS Test From: Richard Gagnon richg_1998@......... Date: Sun, 19 Sep 2004 19:02:42 -0700 (PDT) I use winoncore12.exe available at; http://www.wmcs.net/download.htm It is labeled GPSOC.exe at this download site. Do a search for winoncore12 and you will find a lot of links. http://search.yahoo.com/search?fr=fp-pull-web-t&p=winoncore12 Richard __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: GT+ Encore GPS Test From: "Larry Cochrane" lcochrane@.............. Date: Sun, 19 Sep 2004 19:11:58 -0700 Rex, My WinPlotGPS program can be used to test out your receiver. See http://www.seismicnet.com/winplotgps/ for more information. -Larry Cochrane Redwood City, PSN ----- Original Message ----- From: "Rex Klopfenstein, Jr." To: Sent: Sunday, September 19, 2004 6:23 PM Subject: GT+ Encore GPS Test Could someone point me to a software package that I could use to verify the operation of my GT+ Encore GPS with TARP Interface board? Its been about 4 years since I have been active on this list. Rex Klopfenstein Bowling Green, OH __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Re: GT+ Encore GPS Test From: sismos@.............. Date: Mon, 20 Sep 2004 05:58:55 +0000 Hello Rex, I like TAC32 http://www.cnssys.com/tac32/ you can use it free for 30 days. Angel Monday, September 20, 2004, 1:23:03 AM, you wrote: RKJ> Could someone point me to a software package that I could RKJ> use to verify the operation of my GT+ Encore GPS with TARP RKJ> Interface board?  Its been about 4 years since I have been active RKJ> on this list. __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Mt St Helens heating up again? From: "Coleman, Allan" allan.coleman@............ Date: Mon, 27 Sep 2004 13:09:41 -0700 All, If you want to see good examples of earthquake swarms, check out the = recent activity occurring on Mt St Helens over the last few days. Some = type of an eruption has been predicted, but nothing like the 1980 event. = Go to: http://www.ess.washington.edu/SEIS/PNSN/WEBICORDER/GREEN/welcome.html Scroll down to: HSR EHZ UW : St. Helens - south-ridge then click = on a date like 09/26/2004. Traffic has been heavy on this Internet site = today, so expect to wait longer than usual for the page to open. Allan Coleman __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Parkfield 5.9 From: "Steve Hammond" shammon1@............. Date: Tue, 28 Sep 2004 10:53:51 -0700 FYI-- Parkfield,CA USA, the long awaited and predicted (by the USGS) earthquake has occurred today (9/28/04) at 17:15:24.0 UTC. initial mag is 5.9. Regards, Steve Hammond PSN San Jose and Aptos __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: RE: Parkfield 5.9 From: "Steve Hammond" shammon1@............. Date: Tue, 28 Sep 2004 11:32:30 -0700 Here are some URL'S relating to the predicted earthquake at Parkfield. http://quake.wr.usgs.gov/research/parkfield/ http://www.geophys.washington.edu/SEIS/PNSN/INFO_GENERAL/eq_prediction.html Regards, Steve -----Original Message----- From: Steve Hammond [mailto:shammon1@.............. Sent: Tuesday, September 28, 2004 10:54 AM To: PSN List Subject: Parkfield 5.9 FYI-- Parkfield,CA USA, the long awaited and predicted (by the USGS) earthquake has occurred today (9/28/04) at 17:15:24.0 UTC. initial mag is 5.9. Regards, Steve Hammond PSN San Jose and Aptos __________________________________________________________ Public Seismic Network Mailing List (PSN-L) Subject: Seisan Query From: "steve Shufflebotham" cellectronic@......... Date: Thu, 30 Sep 2004 17:24:27 +0100 Hi All, is there anyone out there who uses Seisan (successfully) with = windows ME. I am experimenting with it, I have Seislog running well on another pc = (OS Win 98), I upload the wav files via network but am having dificulty = viewing them. I have added 2 lines to autoexec.bat as stated in Seisan manual, I must = be doing something wrong, any ideas ? anyone?? Regards, Steve=20
Hi All, is there anyone out there who = uses Seisan=20 (successfully) with windows ME.
I am experimenting with it, I have = Seislog running=20 well on another pc (OS Win 98), I upload the wav files via network but = am having=20 dificulty viewing them.
I have added 2 lines to autoexec.bat as = stated in=20 Seisan manual, I must be doing something wrong, any ideas ?=20 anyone??
Regards, Steve=20
Subject: Re: Seisan Query From: sismos@.............. Date: Thu, 30 Sep 2004 12:19:10 +0000 Hello Steve, I do lots of Seisan / Seislog stuff. I won't say here what I think of ME but I will say that I only use W2000. What is Seisan not doing? What module?? How are you trying to view the wave files?? angel Thursday, September 30, 2004, 4:24:27 PM, you wrote: sS> Hi All, is there anyone out there who uses Seisan sS> (successfully) with windows ME. sS> I am experimenting with it, I have Seislog running well on sS> another pc (OS Win 98), I upload the wav files via network but am sS> having dificulty viewing them. sS> I have added 2 lines to autoexec.bat as stated in Seisan sS> manual, I must be doing something wrong, any ideas ? anyone?? sS> Regards, Steve -- Best regards, sismos mailto:sismos@.............. __________________________________________________________ Public Seismic Network Mailing List (PSN-L)