PSN-L Email List Message

Subject: Re: Strange geophone pattern
From: "Geoff" gmvoeth@...........
Date: Thu, 11 Sep 2008 18:32:11 -0700

I have found one MUST have a physically isolated plat form
independent of everything that moves including tree roots.
For your seismometer to rest on. two or three feet
underground using a granite tile resting on three
surveyor stakes driven three or more feet into the ground
works the best for myself.
Everything glued down with Goop or something like it.
Human artifacts are a terrible distraction and periodic
things are most likely human generated like air conditioners
and refridgerators.
The colder your climate the deeper you should go.
Bedrock platform (Like Granite) being the best possible.
Good Luck Comrade.
----- Original Message ----- 
From: "Steinar Midtskogen" 
Sent: Thursday, September 11, 2008 1:36 AM
Subject: Strange geophone pattern

>I have a Mark Products 4.5 Hz 3 component L15B geophone, and since the
> two major earthquakes in Indonesia and Hokkaido happened during the
> night here when the local noise is low, I thought it would be
> interesting to see whether such quakes show up at all on a geophone.
> Apparently, they didn't, but I found a strange pattern repeating every
> 25 minutes:
> Does anyone have any ideas what could cause this?
> Perhaps an airconditioner two floors above?  Then it seems to run
> through some kind of program that I wasn't aware of.  Or perhaps a
> neighbour runnings some kind of machinery going through cycles?
> The datalogger is fanless and diskless, so it shouldn't cause any
> vibrations.
> -- 
> Steinar
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