Between distances of around 100-800 km you may see a refracted P wave.  I =
believe it is referenced as a Pn wave.  The refracted P wave will arrive =
before the true P wave.  If you are using Larry's Winquake, that phase is =
available in the tables.  Be sure to turn on Sn as well.

I'm doing this from memory, so don't hold it against me if that isn't =
exactly correct.

Dave

>>> "Steve Hammond"  09/02/09 11:06 PM >>>
I also noticed an anomaly in local events within 20-25km south of my old =
San
Jose location when I lived in south San Jose. My house was located between
the San Andreas and Calaveras faults and I had data from both faults that
had something going on just before the P wave arrived. I showed John Lahr
the data and asked if there was such a thing as  a  pre-P wave and he told
me there was not. I finally figured that it was a just a flaw in the =
sensor.


Regards, Steve Hammond

From: psn-l-request@.............. [mailto:psn-l-request@............... =
On
Behalf Of Barry Lotz
Sent: Wednesday, September 02, 2009 6:54 PM
To: psn-l@..............
Subject: Re: ARRIVAL TIMES: Quiet Before The Storm

=20


Geoffrey
I've also noticed this for quite some time. I thought it was my sensors.
Maybe not.
Regards
Barry


--- On Wed, 9/2/09, Geoffrey  wrote:


From: Geoffrey 
Subject: ARRIVAL TIMES: Quiet Before The Storm
To: "PSN-LIST" 
Date: Wednesday, September 2, 2009, 5:50 PM

I have noticed in some Earthquakes you seem to notice
a short increase in quietness just before the impulse arrives.

Is this a real phenomena or simply a coincidence ?

Does this mean the real arrival time is
the beginning of the noticeable quiet ?

WHY THE QUIET ??
What physics would possibly muffle the noise ?

arrival of Possibly eP instead of simply P ?

Also,

What is the preferred format for a PSN files data ?
FLOAT or INTEGER
16 bit or 32 ?

My data is all 8 bit So should I expand it to
meet the new format ?

Comments ?

geoff
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=20


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