Hi  Jón

I have a similar noise problem with my 4.5 hz geophone
system that is resting on my basement office slab about
20m from a major highway.

I am using Amaseis freeware for data logging and display,
and I generally set the helicorder display low-pass filter
to 1 Hz, and that gets rid of a lot of the local noise.

When I receive and email notice of a teleseismic event,
I look at the data segment even if it does not show
up on my  helicorder display.  Often I can FFT the data
segment, see the quake spectral peak, and apply a bandpass
filter to bring the quake out.

One test to see if your electronics is working well is to
see if you can pick up the ~0.2 Hz  microseism peak on
your geophone system.  My system can generally pick
this up since I started using an AD8626 autozero opamp,
a pcb with star ground configuration, and a shielded
enclosure for my electronics and geophone.

Ciao,

Dave
http://www.infiltec.com/seismo



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