On 2/15/2013 6:33 PM, Brett Nordgren wrote:
> 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
>>
>
>
> __________________________________________________________
>
> Public Seismic Network Mailing List (PSNLIST)
>
> To leave this list email PSNLIST-REQUEST@.............. with the body 
> of the message (first line only): unsubscribe
> See http://www.seismicnet.com/maillist.html for more information.
>
Well, I am glad to see the comment. I noticed that activity myself, but 
blamed it on winter storm development off SW Alaska, Great Lakes and SE 
shore of Greenland. When you see the red color in these areas (for high 
waves), you are getting strong ocean storms. My Lehmans pick it up. 
Chris started me watching these areas a couple of years ago. The storms 
were early this year and the air was colder and denser than usual. In 
fact, my lake froze over earlier than it ever has. There was one 
incident this last month when the Atlantic and Pacific Ocean was quiet 
and the Great Lakes had strong winds....sure enough, the Lehmans picked 
it up.  The bigger hurricanes do about the same. The one that hit 
Galveston and came up the Ohio River Valley registered here from 
mid-Gulf of Mexico until it passed here and went on to New York State.

  I just went back randomly choosing Jan 9 at 1:30 UTC and got a FFT 
peak at .15 Hz on both Lehmans(peaking at 100 on (vertical scale)the E-W 
and 50 plus on the N-S) and Nov 30 of last year the peak was between .1 
& .3 hz and up to 100 vertical scale (N-S) and about the same on the 
E-W.                            Tom D
__________________________________________________________

Public Seismic Network Mailing List (PSNLIST)

To leave this list email PSNLIST-REQUEST@.............. with 
the body of the message (first line only): unsubscribe
See http://www.seismicnet.com/maillist.html for more information.