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Entry  Sun May 30 22:18:49 2010, rana, Update, PEM, Granite slab w/ lead balls is so far a flop 
    Reply  Mon May 31 22:52:57 2010, rana, Update, PEM, Granite slab w/ lead balls is so far a flop Untitled.pnghuddlez.pnghuddlez.png
Message ID: 3018     Entry time: Sun May 30 22:18:49 2010     Reply to this: 3022
Author: rana 
Type: Update 
Category: PEM 
Subject: Granite slab w/ lead balls is so far a flop 

The seismometers showed an increased noise in the Y-direction when put on top of the granite slab. By tapping the slab, you can tell that its really a mechanical resonance of the lead balls + granite system at ~15-20 Hz.

I tried new balls, flipping the slab upside down, and sitting on the slab for awhile. None of this changed the qualitative behavior, although each of the actions changed the resonance frequencies by several Hz.

I have removed the granite/balls and put the seismometers back on the linoleum floor. The excess noise is gone. I have put the new big box back on top of them and we'll see how the data looks overnight.

 

I expect that we should remove the linoleum in a wider area and put the seismometers directly on the floor.

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