Bob & Geoff,

I'd missed that part of the original question, and Bob is quite 
right.  Gravity (an acceleration) and the ground motion you want to 
see (which may also be viewed as acceleration) can't be separated 
from each other.  When you manage to cancel out the first one, you 
also end up canceling out the second.  Unfortunately, no way around it.

Gravity is just a (huge) DC component of the same motion you want to measure.

Brett

At 01:55 PM 2/29/2012, Bob McClure wrote:
>Hi Geoff,
>
>Making the mass of a seismometer neutrally buoyant will get you 
>nowhere. The mass will not differentially move with respect to the 
>frame when external acceleration is applied. You may be able to 
>demonstrate a long period, but you will get no signal.
>
>Bob
>
>On Wed, Feb 29, 2012 at 1:40 PM, gmvoeth 
><gmvoeth@.........> wrote:
>Hello Mr. Nordgren,
>
>You speak in a way I might be able to understand.
>
>What I was wondering is that buoyancy can be implemented in ways
>which might produce spring like results possibly one might
>use a "weak spring (low weight/inches)" with whatever mass
>in combination with buoyancy "like a submarine or ship" to
>produce extended or lower frequencies using shorter lengths.
>simply submerging the mass within a dense liquid may allow
>this to happen.
>
>has such a thing ever been tried ?
>
>I saw this research ship which could be flooded
>to float like a fising bobber ? it made me think
>of other things like this one above.
>
>thanks for your responses.
>
>regards,
>geoff


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