Hi Richard,

I agree with the various comments  -- a small 10 Hz geophone is not going
to work very well for small, regional events.  There are two problems:  1 - the
natural frequency of 10 Hz is a bit high (2 Hz would be better) and 2 -
the sensitivity, even at 10 Hz is not great, as these are very small units
designed to pick up rather large signals.

Having said that, the price is right and it couldn't hurt to give them a
try.  You would need to set up a filter/amplifier/recorder system to test
them out and during the test you could be building a Lehman or purchasing
a lower frequency geophone.

Cheers,
John
At 11:48 PM 6/24/2003, you wrote:
>Jim,
>
>Thanks for the comments. About the frequency response. Are these
>geophones
>damped to such a large extent that even if I roll off the output at,
>say,
>10 Hz, I still wouldn't have anything resembling a useful output? I only
>intend these to monitor local events. I've figured it easier to first
>look
>at local events with commercial sensors and work on the electronics and
>data gathering/recording. Later I do intend to construct some other
>sensors for teleseisms.
>
>Thanks again,
>
>Richard
>
>Jim ODonnell wrote:
> >
> > Hi Richard-  The Geosource is a good geophone, but not adequate for
> > earthquake recording, too high a frequency response at 14 Hz, you will
> > need the 4.5 Hz or 1 Hz response.  Your questions and many more you have,
> > can be anwsered by going to the Public Seismic Network web page-
> > http://psn.quake.net/geophone/index.html for geophones that can record
> > earthquakes.
> >
> > More general information is at:  http://psn.quake.net
> >
> > Yes Pleasanton is an active area...
> > Best Regards-
> > Jim O'Donnell
> > UNLV
> > On Mon, 23 Jun 2003 22:55:20 -0700 Richard Schwaninger
> >  writes:
> > > Hello group.
> > >
> > > 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
> > > google.
> > >
> > > 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.
> > >
> > > Richard
> > >
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