PSN-L Email List Message

Subject: Re: Strange chirps in event data?
From: Larry Conklin lconklin@............
Date: Sat, 23 Jul 2011 16:36:17 -0400


Well, whatever it is that I'm seeing, I'm very sure it has nothing to do 
with the quake.  The signal isn't natural looking at all.  It is a 
nearly sinusoidal wave that begins pretty abruptly, sweeps down in 
frequency from 2 hz to 0.4 hz and then stops fairly abruptly.  I have a 
history of similar artifacts that have showed up from time to time, but 
I don't think they have shown this sort of frequency sweep before.  That 
is what caught my interest this time.  In past occurrences I would see a 
minute or so of a very pure looking tone that would show up in the FFT 
plot as a very narrow spike around 2 hz.  I'd love to know what's going 
on, but don't have much of an idea of how to run it down.

Larry


> both of my Leymans show a sharp spike about 25 seconds before S 
> arrival here in Evansville, IN...largest spike occurred on my E-W unit 
> it is visible on the N-S and vertical AS-1 to lesser extent.
__________________________________________________________

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.

[ Top ] [ Back ] [ Home Page ]