Geoff -

You are correct about the background noise.  For more information,.  I  
would suggest that you download and read the following article from  
the Albuquerque Seismological Laboratory:

	OFR 93-322:  Observations and Modeling of Seismic Background Noise    
Use the following link:

	http://earthquake.usgs.gov/regional/asl/pubs/files/ofr93-322.pdf

On page 14, the report states:

"...the most dominate features [Earth Noise] being the natural  
microseisms in the period range from about 1 to 20 sec with peaks at 5  
sec and 18 sec, and the Earth tides with peaks at semi-diurnal and  
diurnal periods.  The rounded low-noise peak in the long-period band  
at a period of about 120 sec appears to be a real and significant  
noise feature, it cause unknown...."

Cheers

Bob Hancock



On Nov 3, 2008, at 8:29 AM, Geoff wrote:

> I have heard "somewhere on the internet" that 5 second period  
> microseismic waves
> are generated by waves in the oceans waters at certain resonant depth
> and radiate for very long distances.
> This has been determined through scientific observations.
> Not to say other phenomena do not also create
> 5 second waves.
> I often see such waves relating to weather fronts coming from
> the pacific before it hits arizona.
> And my system was designed only to see
> 3 second to 2Hz range so they must be
> quite large in magnitude.
> Its not weather over land but weather over ocean.
> geoff
>
>>
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