I have often thought it would right
to cut a hole in the slab and drill down a few
feet then set the geophone on a post that
has been driven a foot or two into the ground
at that location but the post must be isolated
from the slab as well as the surrounding hole.
I have seen vibration isolation slabs in
microciruit manufacturing labs
so that their photo whatever will
stay as still as possible.

----- Original Message ----- 
From: "Dave Nelson" 
To: 
Sent: Saturday, January 06, 2007 3:10 PM
Subject: Re: Geophone with long legs


yes Jon

   it MUST be in good contact with the ground to record ground motion properly.

    if it is just sitting on the floor of the house or as sounds like, on
legs above the floor
then most of anything it will record will be house/floor movement.

   if it must be brought closer to the house, then either bury it under the
house if there is underfloor access.  if ur house is on a concrete pad then
its going to have to go outside beside the house.
   Either way its still going to record a lot of building movement and
movement of people from within the house

cheers
Dave N
Sydney, Oz



At 01:19 PM 6/01/2007 +0000, you wrote:

>Hi all
>
>I am wondering, since I did move my geophone back inside, is the
>geophone less sensitive becose he now stands on the legs but is not
>surrounded in sand like when I did have him outside. Does it matter in
>the terms of detecting earthquakes ?
>
>Regards.
>--
>Jón Frímann
>http://www.jonfr.com
>http://www.simnet.is/jonfr500/earthquake/
>
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