From looking at your pictures and FFT, I wondered if all of your
components are either securely assembled or placed on three point
mounts

Four point mounts or components resting on flat surfaces can be
unexpected balanced between two semi-stable positions.

I did use four pivot points on the Lehmans...a mistake I won't make again 
.... the bases for the Lehmans are 1/4" steel these could be used as boat 
anchors ... unfortunately I sold the boat!  The support of the mental plates 
that hold the magnets isn't as stable ... this could be an issue. But the 
peaks at 4 hz is gound on the geophone buried outside!

If so, the microsiems or quakes can move the components between those two 
positions
resulting in high frequency noise

.. The AS-1 uses a knief edge rather than a hinge. The AS-1 sits in an old 
refrigerator with the door closed. The pivot point on the booms of the 
Lehmans is a stainless steel ball bearing. The only issue I haven't 
addressed is that the Lehmans sit on concrete blocks sitting on the concrete 
floor. From what you infer, this might be an issue. I raised the Lehmans up 
off the floor so that I didn't have to bend over as much.

.
I collected one hours noise from this morning.

Mine are one minute but it would help know where you two are....??? 
Georgia??? Macon ...right?
You could test the electronic noise by locking the seismometer.  I would
not expect much noise from electronics compared to the noise that will
come from the seismometer output.

suggestion under advisement

This issue has been around for some time. I even sent one amp board back to 
Larry for him to look at. I put an isolation transformer and battery back up 
to help smooth out the AC. I even had the local electric company come 
out(firends in the right places) with special equipment and test the 
incoming AC...nothing serious there.
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