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
Thomas,
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.
Regards,
Brett
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.
>
>http://sincedutch.wordpress.com/2012/11/30/11302012-strange-vibrations-detected-throughout-the-united-states/
>
>There were a whole bunch of these "stories" in December
>
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