Hi

I would like to add to the history being=20
discussed. I am quoting all the previous posts so=20
the entire history will be in one spot. Sorry for the large email.

I wanted to add some information about Howard=20
Grebin. I am deeply in debt to Howard and to his=20
family as I obtained two of his Geotech 8700=20
seismometers he bought as surplus from the U of=20
Calif. Berkeley seismic lab and his drum=20
recorder. His story is also amazing as he=20
collected parts from all over to build his=20
systems. One story in particular I wanted to=20
share was that he bought the seismometers from a=20
junk dealer after they had the lead weights=20
removed and he collected auto wheel balancing=20
weights from the streets and re-melted them to cast new weights!

I have a full folder of information from Howard=20
that I am preserving that has schematics of=20
amplifiers, and newspaper interviews etc., if=20
anyone is interested in further info.

George

At 03:39 PM 4/27/2012, Stephen Hammond wrote:
>Chris, sorry for all the typos as I hit a button=20
>and off the response went. So if you would,=20
>please just read between the gaps and over the=20
>wrong words as I did not edit it in any way=85  To=20
>try and answer the remainder of your questions:=20
>As for a selection of seismometers, The Lehman=20
>design was best because as it only took simple=20
>tools to build one. As you may already know the=20
>Professor that designed it and published the=20
>original Scientific America plans is also a=20
>member of this group. In the photo of your=20
>system below you provided, which I have looked=20
>at and admired many times before, it provides a=20
>good example of what you can build once you have=20
>mastered the original Lehman design.  As for the=20
>amp design, as I said below, Pete Rowe provided=20
>a detailed two page design for building=20
>amps/filters and gave the design  freely to the=20
>group. There has never been a lot of planning=20
>for any one aspect of the sensors people use,=20
>just a lot of experimentation. For example, I=20
>once built a Lehman for $5 from a toilet tank=20
>float filled with water and a brass rod. Ed=20
>Cranswick told me to keep the cover down on the=20
>enclosure if anybody dropped by to see my=20
>insulation=85 There was a member the contributed=20
>in the early days. One by the name of Sam Gazdic=20
>in Oakland, CA who provided a lot of information=20
>about sensors and systems. He worked for the=20
>State of California and became a valuable=20
>resource when you had a question about=20
>commercial seismographs. Bob Ogburn was in the=20
>National Guard and worked in electronics in the=20
>Valley. He developed an array of sensors using=20
>4-inches of PVC pipe filled with oil for damping=20
>and =BD of a flutter fan from the old Apple=20
>cooling systems fans. Then there were also the=20
>real old-timers Howard and Woody; the first=20
>=93public citizens=94 to install and run seismic=20
>sensors in their homes. Howard and Woody never=20
>formally joined the PSN meetings but they did=20
>help with pen motors, chart recorders and=20
>sensors. They lived in the North Bay and in the=20
>40=92s were running seismographs and chart=20
>recorders. (I think the Sprengnether Jan Froom=20
>is letting me use actually belonged to Woody=20
>before he passed? Anyway-- ). Howard told us=20
>over lunch one day that Offenhauser at the=20
>Berkeley Seismology Lab would call them in the=20
>40=92s after WWII to see if they recorded an event=20
>and to argue over the magnitude. Woody had the=20
>best seismic shed/workroom that I have ever=20
>seen. He had his cart reorders, HAM radio=20
>equipment and workbenches all neatly laid out=20
>with seismic traces and travel time charts on=20
>the walls. It was the kind of place you could=20
>just hangout in for days at a time.
>
>I think the thing about the PSN I like the best=20
>is that is continues to provide a framework=20
>where people to can share information and ideas.=20
>There are really only two rules in the PSN that=20
>we all agreed upon. (1) Don=92t have any rules.=20
>(2)Never have a meeting more than once a year.=20
>When BBS=92s were being replaced with Internet=20
>websites Larry said he wanted to develop a web=20
>presence which he did. Larry=92s contributions has=20
>enabled people all over the world to join in on=20
>what started as a local Bay Area thing. As you=20
>already know the PSN is a worldwide organization=20
>and I feel that it sets a good example by=20
>showing what can be accomplished when people=20
>come together with respect and an openness to communicate and share.
>
>Thanks for your note, I hope I answered your=20
>questions. Regards, Steve Hammond PSN San Jose, Aptos CA
>
>From: psnlist-request@.................
>[mailto:psnlist-request@............... On Behalf Of Stephen Hammond
>Sent: Friday, April 27, 2012 1:17 PM
>To: chrisatupw@.......
>Cc: psnlist@..............
>Subject: RE: Peoples Seismograph Array ---> Public Seismic Network
>
>Hi Chris, Thanks for your note and all the=20
>references. As for the Lehman=92s I currently=20
>have, I=92m very unhappy with them and they are=20
>headed for scrap. When I was in San Jose I had=20
>40CM booms and they worked very well and had=20
>25-30 second periods. I had to cut the booms=20
>down due to space issues on my small property=20
>here in Aptos, after moving  from San Jose and=20
>the periods went from  30 second to 10. I also=20
>live uphill from Monterey Bay and the waves to=20
>my west and the main street to the east create=20
>lots of noise. So I have to deal with that a lot=20
>of times and when the storms come in the=20
>Lehman=92s are unusable.  Jan Froom just lent me=20
>a  Sprengnether  which is running after being=20
>rebuilt at this point and I=92m still testing the=20
>lower pivot I built for it. If you look at AT2=20
>on-line over the last week or two you will see=20
>the Sprengnether at a gain of 210.  I=92m still=20
>waiting for the first local event. The period is=20
>not too long at this point. I think I need to=20
>pull it apart again and tweak the position of=20
>the pivot  as one of the two cylinder magnets is=20
>too close to the coil. When the Springnether=20
>gets going I=92m pulling the two Lehman=92s. The cup=20
>/ point lower pivot has never worked that well.=20
>I already have three HS10=92s which were=20
>originally in the old Cal-Net run by the USGS.=20
>They work really well. As for the amp and filter=20
>designs, they came from Pete Rowe in 1990 and=20
>are on the San Jose PSN site. Ted Black wrote=20
>the original PSN code and we built or own A/D=20
>boards and wrote our own hardware interface=20
>drivers in Assembler. Later, after Larry joined,=20
>he developed his hardware data collection  and=20
>software and I continue to us it today.
>
>About the history:  As Ed Cranswick told the=20
>story over beers several times he needed a grant=20
>to go to the AGU meeting that year and he=20
>published the =93Peoples=94 Seismic Array paper (=20
>which is listed in the link you provided) so he=20
>could attend the meeting and present his paper.=20
>He and Phil (a software engineer) had been=20
>working together on a number of projects and  If=20
>I remember correctly it did have something to do=20
>with his work in Turkey or Russia but I=92ve lost=20
>that point and can=92t recall it. Anyway, Ed got=20
>his funding and went to the AGU meeting with=20
>Phil and Ed presented their work. Like I SAID,=20
>IT HAD ABSOLUTLY NOTHING TO DO WITH US. Than in=20
>Oct. 1989 the Loma P event went off in Aptos=20
>(Santa Cruz County) and it sparked a lot of=20
>interest in seismology. However, before Oct/89=20
>inside IBM there was a group of people that had=20
>been working on their hobby, not a formal IBM=20
>product,  which was seismology instrumentation.=20
>Jan From, Ted Blank, Dick and one outsider, Pete=20
>Row had already hooked-up and were sharing=20
>information. Jan was a tools programmer for IBM=20
>and wrote the software to float a 3,000 pound=20
>block of granite on streams of air so that=20
>master servo tracks could be written error free=20
>on large DASD packs and lived in Gilroy, CA. Ted=20
>Blank was IBM=92s performance export for the MVS=20
>operating system and lived in New York and=20
>worked at the Poughkeepsie, NY plant. Pete Row=20
>was a contractor and worked on secret=20
>electronics government projects here in San=20
>Jose, CA. Ted had written his SDAS software for=20
>data collection on a PC and had built from the=20
>1956 plans a Lehmann seismograph. Jan had=20
>communicated via IBM=92s internal discussion=20
>network and gotten the software and info from=20
>Ted and shared it with Pete as they were HAMs on=20
>the local 2m radio network and both had built=20
>and operated seismic stations. They would share=20
>info and data via the local 2m network here in=20
>San Jose run by Bruce Kenny (W6TED). I (and 250=20
>other people) was working on developing IBM=92s=20
>OSI software product at the IBM Scientific=20
>Center in Palo Alto and lived I lived in south=20
>San Jose. Jan shared his plans and Ted=92s=20
>software with me and I built a Lehman and hooked=20
>it to a PC via an A/D board and amp I built from=20
>sample chips I got from local vendors. Dick=20
>Chelberg was an engineer working in the IBM=20
>plant developing DASD in  San Jose and as a side=20
>profession operated a complete machine shop at=20
>his home. He had machined a Lehman and was also=20
>using Ted=92s software and an IBM A/D card to=20
>collect seismic data. One Saturday morning=20
>following we got together for coffee and donuts=20
>at my home to meet face to face and talk about=20
>seismographs and share info. As we were all=20
>using Ted=92s software we needed a way to share=20
>the datasets so I volunteered to install a BBS.=20
>Within a few weeks it was operational and the=20
>IBM Think Magazine folks got wind of this=20
>seismic group operating in San Jose and asked to=20
>write an employee focus item for the Company=20
>Think Magazine and they interviewed each of us=20
>and wrote the article. The interesting thing was=20
>tha6t totally unrelated, Ed=92s AGU paper was=20
>discussed in the San Jose Mercury News. And on=20
>that Saturday morning we had kicked around a few=20
>names for the BBS and it ended up being named=20
>=93THE =93PUBLIC=94 SEISMIC NETWORK=94 in San Jose. So=20
>when we read about ED I called him at the USGS=20
>in Menlo Park and  the next day he showed up at=20
>my house to see what we were doing. From that=20
>point on our relationship grew with lots of=20
>support from the USGS and lots of great advice.=20
>John Lahr, Ed and two other=92s stared to attend=20
>our meetings and as the word about the PSN got=20
>around more and more people in the Bay Area=20
>started to join the group. So did the BBS=20
>network. Jerry and Dorothy Darby were part of=20
>the 2M radio group in Pasadena and they=20
>installed a PSN BBS and were linked them=20
>together with nightly mail runs and file=20
>sharing. They also were operating seismographs=20
>at their home as were a number of folks in the=20
>LA area. Charlie Daniels In Memphis, TN had a=20
>seismograph and installed the PSN BBS in=20
>Tennessee and link it into our network. The=20
>folks at CERI also supported his site and gave=20
>him access to info on New Madrid. Allen Lynn was=20
>the Station Chief at the USGS in Menlo Park and=20
>asked me to install a PSN BBS in his office.=20
>Latterly, on top of a filing cabinet in his=20
>office, which I did.  I maintained it via=20
>FTP  and later John Lahr took over its=20
>operation. So the original PSN network was a=20
>four-node BBS network and the members could post=20
>mail and event files to any of the systems and=20
>in turn a number of elementary schools and high=20
>schools started using the systems in their=20
>course work. I helped to install systems and=20
>seismographs at MT View and Los Altos high=20
>schools and Anderson Elementary in San Jose. Jan=20
>installed systems at the Gilroy Middle school=20
>and today created and maintains the seismic=20
>system and Gilroy Gardens. Pete and Ted are=20
>still active here on the list and the last time=20
>I check, Bruce and Dick lived here in CA. Ed=20
>Cranswick was in Australia and we are still=20
>arguing over who was first, the Peoples or=20
>Public Seismic Network. I=92ll have to check the publication dates to see.
>Regards, Steve Hammond PSN San Jose, Aptos, CA
>
>From: chrisatupw@....... [mailto:chrisatupw@........
>Sent: Thursday, April 26, 2012 5:59 PM
>To: shammon1@.............
>Subject: Peoples Seismograph Array ---> Public Seismic Network
>
>Dear Steve Hammond,
>
>**** Edward Cranswick wrote:=20
>http://dominicapsn.=
freeyellow.com/PSN/PSN_History.html=20
>back in 1996
>regarding the PSA / PSN history. But the=20
>attached EOS supplement is dated 1990.
>     It looks like the Peoples Seismic Array=20
> project was first considered in 1985 ?
>     Larry Cochrane's first PSN Internet file was in the 4th quarter of=
 1995
>
>
>
>
>      I have spoken to Larry and he suggested contacting you regarding the
>
>historical development stages of PSA / PSN=20
>before 1996. What were the plans for
>
>the seismometers, please ? Or were you planning=20
>to use extended period geophones ?
>
>How did the proposals develop please ?
>
>
>     I visited your web site and noted that both Lehmans were set at 12
>
>seconds period. This is much less than the 25 to 30 seconds that we use
>
>to match the Love waves and I wondered why you had chosen it, please ?
>
>The boom length of 30 cm is much shorter than we usually use.
>
>
>
>
>Our Seismometer developments
>    Point in a cup and knife edge "bearings" are both fundamentally flawed
>
>designs. I suspect that the idea of using "knife edge" bearings may have
>
>originated from chemical balances - but their bearings are ONLY CALLED that=
 !
>
>The Agate bar is cut and polished with 60 degree corners, but the bearing
>
>corner was then carefully lapped to a tiny cylinder to take the rated load
>
>--- of just 200 gm !! A razor sharp Agate edge would shatter easily.
>
>
>
>     Two bearing types which WILL take typical=20
> seismometer loads of several kg
>
>are a plane rolling on a ball - in my case a section of a SS scalpel blade=
 on
>
>a SS ball bearing - and crossed cylinders. These=20
>can be hardened EN57 steel rod,
>
>or more usually tungsten carbide rods. Tungsten=20
>carbide needle roller bearings are
>
>produced. You can buy 1/8" OD tungsten carbide=20
>drills and use the shank ends, but
>
>there are plenty of small WC milling cutters=20
>with parallel shanks. I got a free
>
>supply of broken cutter shanks from a small=20
>engineering business just by asking !
>
>
>
>     I described the test results of these and=20
> of rolling foil and wire very low
>
>dynamic loss, high load flexures in a paper in=20
>ArchivX. The traditional crossed
>
>foil and wire type suspensions show energy loss and noise due to the=
 flexure
>
>being bent very close to the clamped ends.
>
>
>
>     Below is a photo of the seismometer that I use
>
>http://=
www.jclahr.com/science/psn/chapman/2008%20lehman/index.html=20
>
>
>     I can set the period to 30 seconds quite easily to sense the Love
>
>waves at their full amplitude. The principle features are a SS scalpel
>
>blade rolling on a 1/2" SS ball bearing lower fulcrum. The V cable top
>
>support prevents the arm from rotating about it's long axis - this can
>
>produce an undamped peak at 3~8 Hz in the FFT display if it is not
>
>suppressed. The quad Neodymium magnet damping and sensor blocks are
>
>highly effective. A 1/16" thick horizontal Copper damping blade is used.
>
>Soft Aluminum can also be used, but it is significantly diamagnetic and
>
>has double the resistivity. It is also relatively difficult to buy. One
>
>advantage of this design is that the magnet block can be slid along the
>
>base bar to cover just as much of the N/S magnet joint as is required.
>
>This butted N/S magnet joint develops a much greater damping force than
>
>a widely spaced poles. The damping force required depends on the period
>
>of the arm as well as on the seismic mass. The sensor block uses 1.5"
>
>long magnets and a rectangular coil. This allows the arm to drift +/-
>
>1/2" without any change in the sensitivity. A relatively few number of
>
>turns is required on the coil - 1,500 to 2,000. The sensitivity is about
>
>20x that of a traditional Alnico U magnet + relay coil.
>
>
>
>     A Manual for the commercial SEP UK school seismometer is at
>
>=20
>http://www.mindsets=
online.co.uk/images/Seismometer.pdf=20
>
>
>     The amplifier band pass is from 0.016 to 5 Hz and the gain can be
>
>switched x100, x200 or x500. The UK is a crowded noisy island with very
>
>few local quakes, so a 5 Hz LP filter is optimal. The period is set by
>
>tilting the base plate and a value of 25 to 30 seconds is usually chosen.
>
>The suspension is 1/8" OD crossed tungsten carbide needle rollers. The
>
>mass is brass. The boom is ~56 cm long. The extended period traces enable
>
>you to pick up at least twice the number of quakes identified by a P&S
>
>wave trigger. You pick out the often large surface waves and then look
>
>for the P&S waves.
>
>     This is a very successful project. Over 400 seismometers have been
>
>sold since Easter 2007.
>
>
>
>     Regards,
>
>
>
>     Chris Chapman MA Oxon (Physics-retired)


George Bush
Sea Ranch, CA, USA
38.737817, -123.488928
Elevation 102'.


Hi 


I would like to add to the history being discussed. I am quoting all the
previous posts so the entire history will be in one spot. Sorry for the
large email. 


I wanted to add some information about Howard Grebin. I am deeply in debt
to Howard and to his family as I obtained two of his Geotech 8700
seismometers he bought as surplus from the U of Calif. Berkeley seismic
lab and his drum recorder. His story is also amazing as he collected
parts from all over to build his systems. One story in particular I
wanted to share was that he bought the seismometers from a junk dealer
after they had the lead weights removed and he collected auto wheel
balancing weights from the streets and re-melted them to cast new
weights! 


I have a full folder of information from Howard that I am preserving that
has schematics of amplifiers, and newspaper interviews etc., if anyone is
interested in further info.


George


At 03:39 PM 4/27/2012, Stephen Hammond wrote:

Chris, sorry for all the typo=
s
as I hit a button and off the response went. So if you would, please just
read between the gaps and over the wrong words as I did not edit it in
any way=85  To try and answer the remainder of your questions: As for
a selection of seismometers, The Lehman design was best because as it
only took simple tools to build one. As you may already know the
Professor that designed it and published the original Scientific America
plans is also a member of this group. In the photo of your system below
you provided, which I have looked at and admired many times before, it
provides a good example of what you can build once you have mastered the
original Lehman design.  As for the amp design, as I said below,
Pete Rowe provided a detailed two page design for building amps/filters
and gave the design  freely to the group. There has never been a lot
of planning for any one aspect of the sensors people use, just a lot of
experimentation. For example, I once built a Lehman for $5 from a toilet
tank float filled with water and a brass rod. Ed Cranswick told me to
keep the cover down on the enclosure if anybody dropped by to see my
insulation=85 There was a member the contributed in the early days. One by
the name of Sam Gazdic in Oakland, CA who provided a lot of information
about sensors and systems. He worked for the State of California and
became a valuable resource when you had a question about commercial
seismographs. Bob Ogburn was in the National Guard and worked in
electronics in the Valley. He developed an array of sensors using
4-inches of PVC pipe filled with oil for damping and =BD of a flutter fan
from the old Apple cooling systems fans. Then there
were also the real old-timers Howard and Woody; the first =93public
citizens=94 to install and run seismic sensors in their homes. Howard and
Woody never formally joined the PSN meetings but they did help with pen
motors, chart recorders and sensors. They lived in the North Bay
and in the 40=92s were running seismographs and chart recorders. (I think
the Sprengnether Jan Froom is letting me use actually belonged to Woody
before he passed? Anyway-- ). Howard told us over lunch one day that
Offenhauser at the Berkeley Seismology Lab would call them in the 40=92s
after WWII to see if they recorded an event and to argue over the
magnitude. Woody had the best seismic shed/workroom that I have ever
seen. He had his cart reorders, HAM radio equipment and workbenches all
neatly laid out with seismic traces and travel time charts on the walls.
It was the kind of place you could just hangout in for days at a time.


 

I think the thing about the PSN I like the best is that is continues to
provide a framework where people to can share information and ideas.
There are really only two rules in the PSN that we all agreed upon. (1)
Don=92t have any rules. (2)Never have a meeting more than once a year. When
BBS=92s were being replaced with Internet websites Larry said he wanted to
develop a web presence which he did. Larry=92s contributions has enabled
people all over the world to join in on what started as a local Bay Area
thing. As you already know the PSN is a worldwide organization and I feel
that it sets a good example by showing what can be accomplished when
people come together with respect and an openness to communicate and
share. 

 

Thanks for your note, I hope I answered your questions. Regards, Steve
Hammond PSN San Jose, Aptos CA

 

From: psnlist-request@..............
[
mailto:psnlist-request@..............] On Behalf Of Stephen
Hammond

Sent: Friday, April 27, 2012 1:17 PM

To: chrisatupw@.......

Cc: psnlist@..............

Subject: RE: Peoples Seismograph Array ---> Public Seismic
Network

 

Hi Chris, Thanks for your note and all the references. As for the
Lehman=92s I currently have, I=92m very unhappy with them and they are heade=
d
for scrap. When I was in San Jose I had 40CM booms and they worked very
well and had 25-30 second periods. I had to cut the booms down due to
space issues on my small property here in Aptos, after moving  from
San Jose and the periods went from  30 second to 10. I also live
uphill from Monterey Bay and the waves to my west and the main street to
the east create lots of noise. So I have to deal with that a lot of times
and when the storms come in the Lehman=92s are unusable.  Jan Froom
just lent me a  Sprengnether  which is running after being
rebuilt at this point and I=92m still testing the lower pivot I built for
it. If you look at AT2 on-line over the last week or two you will see the
Sprengnether at a gain of 210.  I=92m still waiting for the first
local event. The period is not too long at this point. I think I need to
pull it apart again and tweak the position of the pivot  as one of
the two cylinder magnets is too close to the coil. When the Springnether
gets going I=92m pulling the two Lehman=92s. The cup / point lower pivot has
never worked that well. I already have three HS10=92s which were originally
in the old Cal-Net run by the USGS. They work really well. As for the amp
and filter designs, they came from Pete Rowe in 1990 and are on the San
Jose PSN site. Ted Black wrote the original PSN code and we built or own
A/D boards and wrote our own hardware interface drivers in Assembler.
Later, after Larry joined, he developed his hardware data
collection  and software and I continue to us it today. 

 

About the history:  As Ed Cranswick told the story over beers
several times he needed a grant to go to the AGU meeting that year and he
published the =93Peoples=94 Seismic Array paper ( which is listed in the lin=
k
you provided) so he could attend the meeting and present his paper. He
and Phil (a software engineer) had been working together on a number of
projects and  If I remember correctly it did have something to do
with his work in Turkey or Russia but I=92ve lost that point and can=92t
recall it. Anyway, Ed got his funding and went to the AGU meeting with
Phil and Ed presented their work. Like I SAID, IT HAD ABSOLUTLY NOTHING
TO DO WITH US. Than in Oct. 1989 the Loma P event went off in Aptos
(Santa Cruz County) and it sparked a lot of interest in seismology.
However, before Oct/89 inside IBM there was a group of people that had
been working on their hobby, not a formal IBM product,  which was
seismology instrumentation. Jan From, Ted Blank, Dick and one outsider,
Pete Row had already hooked-up and were sharing information. Jan was a
tools programmer for IBM and wrote the software to float a 3,000 pound
block of granite on streams of air so that master servo tracks could be
written error free on large DASD packs and lived in Gilroy, CA. Ted Blank
was IBM=92s performance export for the MVS operating system and lived in
New York and worked at the Poughkeepsie, NY plant. Pete Row was a
contractor and worked on secret electronics government projects here in
San Jose, CA. Ted had written his SDAS software for data collection on a
PC and had built from the 1956 plans a Lehmann seismograph. Jan had
communicated via IBM=92s internal discussion network and gotten the
software and info from Ted and shared it with Pete as they were HAMs on
the local 2m radio network and both had built and operated seismic
stations. They would share info and data via the local 2m network here in
San Jose run by Bruce Kenny (W6TED). I (and 250 other people) was working
on developing IBM=92s OSI software product at the IBM Scientific Center in
Palo Alto and lived I lived in south San Jose. Jan shared his plans and
Ted=92s software with me and I built a Lehman and hooked it to a PC via an
A/D board and amp I built from sample chips I got from local vendors.
Dick Chelberg was an engineer working in the IBM plant developing DASD
in  San Jose and as a side profession operated a complete machine
shop at his home. He had machined a Lehman and was also using Ted=92s
software and an IBM A/D card to collect seismic data. One Saturday
morning following we got together for coffee and donuts at my home to
meet face to face and talk about seismographs and share info. As we were
all using Ted=92s software we needed a way to share the datasets so I
volunteered to install a BBS. Within a few weeks it was operational and
the IBM Think Magazine folks got wind of this seismic group operating in
San Jose and asked to write an employee focus item for the Company Think
Magazine and they interviewed each of us and wrote the article. The
interesting thing was tha6t totally unrelated, Ed=92s AGU paper was
discussed in the San Jose Mercury News. And on that Saturday morning we
had kicked around a few names for the BBS and it ended up being named
=93THE =93PUBLIC=94 SEISMIC NETWORK=94 in San Jose. So when we read about ED=
 I
called him at the USGS in Menlo Park and  the next day he showed up
at my house to see what we were doing. From that point on our
relationship grew with lots of support from the USGS and lots of great
advice. John Lahr, Ed and two other=92s stared to attend our meetings and
as the word about the PSN got around more and more people in the Bay Area
started to join the group. So did the BBS network. Jerry and Dorothy
Darby were part of the 2M radio group in Pasadena and they installed a
PSN BBS and were linked them together with nightly mail runs and file
sharing. They also were operating seismographs at their home as were a
number of folks in the LA area. Charlie Daniels In Memphis, TN had a
seismograph and installed the PSN BBS in Tennessee and link it into our
network. The folks at CERI also supported his site and gave him access to
info on New Madrid. Allen Lynn was the Station Chief at the USGS in Menlo
Park and asked me to install a PSN BBS in his office. Latterly, on top of
a filing cabinet in his office, which I did.  I maintained it via
FTP  and later John Lahr took over its operation. So the original
PSN network was a four-node BBS network and the members could post mail
and event files to any of the systems and in turn a number of elementary
schools and high schools started using the systems in their course work.
I helped to install systems and seismographs at MT View and Los Altos
high schools and Anderson Elementary in San Jose. Jan installed systems
at the Gilroy Middle school and today created and maintains the seismic
system and Gilroy Gardens. Pete and Ted are still active here on the list
and the last time I check, Bruce and Dick lived here in CA. Ed Cranswick
was in Australia and we are still arguing over who was first, the Peoples
or Public Seismic Network. I=92ll have to check the publication dates to
see. 

Regards, Steve Hammond PSN San Jose, Aptos, CA

 

From: chrisatupw@.......
[
mailto:chrisatupw@.......] 

Sent: Thursday, April 26, 2012 5:59 PM

To: shammon1@.............

Subject: Peoples Seismograph Array ---> Public Seismic
Network

 

Dear Steve Hammond,

 

**** Edward Cranswick wrote:

http://dominicapsn.freeyellow.com/PSN/PSN_History.html back in 1996


regarding the PSA / PSN history. But the attached EOS supplement is dated
1990. 

    It looks like the Peoples Seismic Array project was
first considered in 1985 ? 

    Larry Cochrane's first PSN Internet file was in the
4th quarter of 1995 




 



     I have spoken to Larry and he suggested
contacting you regarding the



historical development stages of PSA / PSN before 1996. What were
the plans for 



the seismometers, please ? Or were you planning to use extended
period geophones ?



How did the proposals develop please ? 



 


    I visited your web site and noted that both
Lehmans were set at 12 



seconds period. This is much less than the 25 to 30 seconds that we
use 



to match the Love waves and I wondered why you had chosen it, please
? 



The boom length of 30 cm is much shorter than we usually use.





 



Our Seismometer developments 


   Point in a cup and knife edge "bearings" are
both fundamentally flawed 



designs. I suspect that the idea of using "knife edge"
bearings may have 



originated from chemical balances - but their bearings are ONLY
CALLED that ! 



The Agate bar is cut and polished with 60 degree corners, but the
bearing 



corner was then carefully lapped to a tiny cylinder to take the rated
load 



--- of just 200 gm !! A razor sharp Agate edge would shatter easily.





 


    Two bearing types which WILL take typical
seismometer loads of several kg




are a plane rolling on a ball - in my case a section of a SS scalpel
blade on 



a SS ball bearing - and crossed cylinders. These can be hardened EN57
steel rod, 



or more usually tungsten carbide rods. Tungsten carbide needle roller
bearings are 



produced. You can buy 1/8" OD tungsten carbide drills and use
the shank ends, but 



there are plenty of small WC milling cutters with parallel shanks. I
got a free 



supply of broken cutter shanks from a small engineering business just
by asking ! 




 


    I described the test results of these and of
rolling foil and wire very low




dynamic loss, high load flexures in a paper in ArchivX. The
traditional crossed 



foil and wire type suspensions show energy loss and noise due to the
flexure 



being bent very close to the clamped ends.




  



    Below is a photo of the seismometer that I
use





http://www.jclahr.com/science/psn/chapman/2008%20lehman/index.html




    I can set the period to 30 seconds quite easily to
sense the Love 



waves at their full amplitude. The principle features are a SS
scalpel 



blade rolling on a 1/2" SS ball bearing lower fulcrum. The V
cable top 



support prevents the arm from rotating about it's long axis - this
can 



produce an undamped peak at 3~8 Hz in the FFT display if it is not




suppressed. The quad Neodymium magnet damping and sensor blocks are




highly effective. A 1/16" thick horizontal Copper damping blade
is used. 



Soft Aluminum can also be used, but it is significantly diamagnetic
and 



has double the resistivity. It is also relatively difficult to buy.
One 



advantage of this design is that the magnet block can be slid along
the 



base bar to cover just as much of the N/S magnet joint as is
required. 



This butted N/S magnet joint develops a much greater damping force
than 



a widely spaced poles. The damping force required depends on the
period 



of the arm as well as on the seismic mass. The sensor block uses
1.5" 



long magnets and a rectangular coil. This allows the arm to drift +/-




1/2" without any change in the sensitivity. A relatively few
number of 



turns is required on the coil - 1,500 to 2,000. The sensitivity is
about 



20x that of a traditional Alnico U magnet + relay coil.





 


    A Manual for the commercial SEP UK school
seismometer is at 



   

http://www.mindsetsonline.co.uk/images/Seismometer.pdf




    The amplifier band pass is from 0.016 to 5 Hz and
the gain can be 



switched x100, x200 or x500. The UK is a crowded noisy island with
very 



few local quakes, so a 5 Hz LP filter is optimal. The period is set
by 



tilting the base plate and a value of 25 to 30 seconds is usually
chosen. 



The suspension is 1/8" OD crossed tungsten carbide needle
rollers. The 



mass is brass. The boom is ~56 cm long. The extended period traces
enable 



you to pick up at least twice the number of quakes identified by a
P&S 



wave trigger. You pick out the often large surface waves and then
look 



for the P&S waves. 




    This is a very successful project. Over 400
seismometers have been 



sold since Easter 2007. 




 


    Regards,





 


    Chris Chapman MA Oxon
(Physics-retired)



George Bush

Sea Ranch, CA, USA

38.737817, -123.488928

Elevation 102'.