PSN-L Email List Message

Subject: RE: Relevelling
From: Dave Nelson davenn@...............
Date: Thu, 31 Jul 2008 18:17:21 +1000

               I agree with Gary,   mounting you system on a wooden floor 
is just a total
  no no ... you are reaslly asking for problems
    You have to do everything you can to get the Lehman sitting on a 
concrete pad
its the only way to get serious stability.   (Keeping in the back of you mind
that even a concrete pad can move a bit with ground swelling etc beneath it.
the larger the pad  the more stable it would usually be)
Even considering that,  the concrete pad will be infinitely more stable.

   Something that Gary didn't mention....   having the sensor elevated off 
the ground
within the building. The sensor is going to record the response of the 
building to
the passing seismic waves, rather than the motion of the ground to those waves.
This of course is not what is wanted.  Your primary mission is to record the
ground motion  NOT the swaying of the building due to seismic waves, wind,
manmade movement  etc.

You have done an excellent job building the Lehman and housing .. don't degrade
the results by poor location  :)

Dave Nelson

At 03:16 PM 7/30/2008 -0700, you wrote:
>I noticed that you have your seismometer mounted on the plywood floor. The
>plywood could be moving as the temperature changes. Is there a way you can
>have it mounted closer to the ground. Do you have a basement with concrete
>floor. This would be better for temperature stability too.


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