PSN-L Email List Message
Subject: Re: Geosource MD-100 geophones
From: John or Jan Lahr johnjan@........
Date: Tue, 24 Jun 2003 05:54:29 -0600
I have some high frequency geophones that were used for refraction.
They are Electr. Syst. Div. Model MD 79, 10 Hz.
There are horizontal and vertical units (which may contain the same
geophones as they may work in any orientation) and I could send you
two horizontals and a vertical for you to try out.
They may work for local events but not teleseisms.
I know that in the central region of the US they used 4.5 Hz geophones
for regional monitoring and did quite well.
Each unit is in a 1-inch diameter cylinder that is 1.25-inches long.
It would be important for your amplifier/filter to have a high gain and to
enhance lower frequencies with at least a one-pole high cut filter corner
at around 2 Hz.
Larry Cochrane could probably give you much more specific advice
based on his experience in Redwood City.
At 11:55 PM 6/23/2003, you wrote:
>I'm new here but have a couple of questions. Please excuse me if this
>has been answered before, I did do a quick search and didn't come up
>with anything. If so please point me to the right place - archive or
>I'm in Pleasanton, and so should have something to look at every once in
>a while. I'm starting to set something up at home. I thought I'd first
>look for local events and so purchased a few Geosource MD-100 geophones.
>They are labeled 14Hz, 330 Ohms.
>Looking at pictures, I've seen similar units arranged in a cluster in a
>X-Y-Z configuration. The MD-100s I have only work in one axis, so I
>figure I will not be able to construct a 3 axis unit with these
>geophones? Is there a work-around? Are there other available (in the $20
>range) units which work on their sides?
>The second question, which really should of been first, is: are these
>geophones adequate or appropriate for monitoring local events?
>Thanks for any information.
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