PSN-L Email List Message

Subject: Re: 8 second Microseisms
From: ChrisAtUpw@.......
Date: Thu, 30 May 2002 21:18:00 EDT


In a message dated 30/05/02, skmort@.......... writes:

> I noticed a strangeness in the background noise today as I was checking my
> traces, so I did an FFT and discovered that they had a period of about 8
> seconds, as compared to the normal 4.5 to 5.5 that I've noticed over the 
> years
> for Northern California!  Anyone have any idea why?  Could this be caused
> by the hurricane, or is something else going on?   

 Hi Stephen,

       The weather in the Atlantic has not been to good lately. Searching 
back through the PSN files turned up a letter from Sean :-

       "Re: 6-second microseisms and hurricanes: An interesting phenomenon in 
the eastern USA is that when a largewind storm due to a deep barometric low 
occurs off the east coast, particularly off of New England, the wave energy 
pounding on the continental shelf propagates through the lithosphere under 
the eastern USA as a 6-second surface wave, at about half the period of the 
oceanic wave. This is also true of any storm off the east coast, except that 
the period will be different, varying from 4 to 10 seconds.  Storms off the 
southwest coast cause a longer storm wave, but the predominant energy is 
still from 5 to 8 seconds." 

       Regards,

       Chris Chapman
In a message dated 30/05/02, skmort@.......... writes:


I noti ced a strangeness in the background noise today as I was checking my
traces, so I did an FFT and discovered that they had a period of about 8
seconds, as compared to the normal 4.5 to 5.5 that I've noticed over the years
for Northern California!  Anyone have any idea why?  Could this be caused
by the hurricane, or is something else going on?   


Hi Stephen,

      The weather in the Atlantic has not been to good lately. Searching back through the PS N files turned up a letter from Sean :-

      "Re: 6-second microseisms and hurricanes: An interesting phenomenon in the eastern USA is that when a largewind storm due to a deep barometric low occurs off the east coast, particularly off of New England, the wa ve energy pounding on the continental shelf propagates through the lithosphere under the eastern USA as a 6-second surface wave , at about half the period of the oceanic wave. This is also true of any storm off the east coast, except that the period will be different, varying from 4 to 10 seconds.  Storms off the southwest coast cause a longer storm wave, but the predominant energy is still from 5 to 8 seconds."

      Regards,

      Chris Chapman

[ Top ] [ Back ] [ Home Page ]