Jim,

Thanks for your message. Answers to some of your questions below....

At 07:14 PM 8/15/99 -0700, you wrote:
>Larry-and PSN Members (The Can-Do Folks),
>
>I am in the process of developing seismic systems (as cheap as possible,
>so I can get them in as many schools as possible) for Clark County
>Schools, here in Las Vegas, which has over 200,00 students.  I am
>thinking along the lines of PEPP, but with a much more affordable system.
> 
>
>Recording at UNLV:
>I recently purchased your Amp/Filter (3 Channels) and the A/D board and
>hooked it up to the UNLV, 20 year old, Lehman (E-W) and 3 S-13's (X,Y,Z).
>The Lehman went thru your Amp/Filter (set at 2K gain) while the S-13's
>went thru a Geotech amplifier of 1K gain, and all 4 were recorded on a
>Gateway PC (8Mb Ram & 400Mb HD) at 50 sps.  I was able to record the
>Scotty Castle sequence (M=5.7, 8/1/99), was I impressed, even the Event
>Detector worked!  Now, all channels went off scale on the Main Shock, it
>appeared either the Amp or A/D clipped on the Lehman, while it appeared
>the S-13 seismometer, it self, was saturated, as the recording was very
>peculiar looking, not the normal clipping.  We were 250 Km's away from
>the epicenter.  The Lehman also has a 10hz oscillation which is small on
>the seismogram and comes out as a spike on the spexa. 
>Question 1.  Is it likely the S-13 seismometer itself would get saturated
>from this Eq ?
>Question 1a.  How do I tell rather the Amp or A/D board clipped?

I don't think the sensor saturated. Its probably too much gain through the
system. 

>Question 1b.  Does the Lehman have another resonant frequency at 10 HZ? 

My Lehman has several resonances. Its hard too say where they will show up.

>
> Geophone Testing (L-4):
> I live about 5 Km's from a recent M=2.5, May 6, which I felt.  UNR has
>two sites 30 Km's and 50 Km's away in opposite directions from Boulder
>City, (BC), (BC is 30km's South-East of Las Vegas), UNR recorded the
>M=2.5, but they need a third site to get a better location.  I hope to be
>that third site to pin down these small shocks which go unnoticed on
>their Network, here in BC.  I just started testing 3 L4's, 2 H & 1 Z,
>here at my house in Boulder City, NV . I have them on my patio with 100'
>of coaxial cable which came with the sensors.  I borrowed them from UNLV
>to determine if they would be good for detecting local EQ's. I put their
>output directly into a DataQ  A/D board, (DI-194, 16 bit, 4 channel, 10V
>FS, sells for $100)  thru the 100' cable, which hooks up externally to my
>PC( HP 96 Mb Ram & 4 GB HD) thru the Com1 port.  I obviously need a
>preamplifier as I don't even see road traffic, they do slightly  pick me
>up when I walk by. 
>Question 2.  What is the L-4 output?

Sorry, I don't know the sensitivity of this sensor.

>Question 3.  Can I use your Amp/Filt board as a Pre-amp? and do I need to
>place it very close to the L4 seismometer to keep a short input cable? 

If your A/D card input is from 0 to 10 vdc and not +-10 vdc there will be a
problem using my Amp card. It produces a +- output voltage. 

>Question 4. Should your  Filter board setting be something like 0.5 to 30
>Hz for the L4.

For geophones I have been using .5 to 20 hz, but I can make it 30 hz if
needed.

>Question 5.  I have a program, Atomic Clock, which calls Boulder or Fort
>Collins, CO to reset my PC clock.  I am wondering if that is
>satisfactory, as my main interest is just S-P values, to locate local
>Eq's. 

Don't know.

>
>At the present time I have the Lehman, 3 S-13's and 2 Z  L-4's recording
>at UNLV using your Amp/filter board on the Lehman and L-4's.  I believe
>you set two of the channels to 20 hz for the Geophones and 10 hz for the
>Lehman. 

Yes, this is correct.

>
>I am ready to order another Amp/Filter board unless someone can suggest a
>cheaper pre-amp.....for the L-4's.
>
>Jim O'Donnell
>Retired Geophysicist

-Larry Cochrane
Redwood City, PSN


_____________________________________________________________________

Public Seismic Network Mailing List (PSN-L)