PSN-L Email List Message

Subject: Re: strange vibrations detected throughout the U.S.
From: Brett Nordgren brett3nt@.............
Date: Fri, 15 Feb 2013 19:33:41 -0500


Sure look like microseisms to me.  Those were from Nov 30, last year, 
and in the winter they can get rather large, and then a few days 
later can almost disappear.

Let's see how big they were:
 From the first chart it looks like they generated a voltage of about 
250 microvolts peak to peak.  Given a typical seismometer sensitivity 
of 1500 Vs/m that implies a velocity of 167 nanometers per second 
p-p.  They had a period of about 7.5 seconds, which is right at the 
microseism frequency peak.  That lets us compute the amplitude of the 
ground motion to be about 200 nanometers p-p.  If the diameter of a 
hair is 70um, then these vibrations were about 1/350 of that 
dimension, completing one vibration every 7.5 seconds.  I doubt if 
very many people could feel that.

I hope someone will check my numbers, but I believe they are not too far off.


At 05:26 PM 2/15/2013, you wrote:
>I guess I have too much time these days. I should go to my underground bunker.
>There were a whole bunch of these "stories" in December


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