PSN-L Email List Message

Subject: Re: Reading a Seismogram
From: George Bush ke6pxp@.......
Date: Wed, 10 Jan 2007 09:46:41 -0800


Larry Cochrane has provided some great tools right in Winquake. He allows
you to see the time of the various phases. To see these, set your P and S
times and than pull-down VIEW, select Phases and click the right button
and click DISPLAY and all of the phases of the various waves are
displayed as labelled red lines on your display. If I see some strong
waves on the graph while using WINQUAKE, I do this and try to understand
what is happening.

At 06:50 PM 1/9/2007 -0700, you wrote: 


Hi Folks,  These questions may have to do with art and experience, as
much as science.  Can one explain how to read a Seismogram, if that is
the correct word?  That is the enlarged section of the recorded trace.  I
normally can find the P and S. I also understand the different
directional movements, as illustrated in pictures I have seen. 


1.  Are the large waves that follow the S, surface waves?

2.  If so can one discern Loves from Rayleigh's, within that section?

3.  Do the Loves and Rayleigh's arrive at different times, as with P and
S? and or, do the look different?


I am sure the more you work with these recordings the better you can
interpret them.


A related question:  I just recorded a very nice image of the 5.7m
01/09/2007 Southeastern Alaska 2259km from Boise Idaho, using my Vertical
Spring sensor.  The best recording, so far,  using this new sensor.   I
was please with the image; a clear P, a smaller but clear S, followed by
a large series of waves, I assume,  to be surface waves. But here I can't
tell a Love from a Rayleigh.   

I did not know a vertical spring sensor would pick up surface waves, even
though the Rayleigh's could move the vertical spring.  Is it that the
vertical is less likely to pick up these waves at greater distances,
because of their longer periods?


Thanks, Ted





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