PSN-L Email List Message

Subject: Re: What are the implications of a M2.8 quake near the San Andreas
From: Mauro Mariotti mariotti@.........
Date: Mon, 19 Jul 2010 09:14:58 +0200


Hello,

from far Italy i guess sharing some experience we have here may be useful.

Single, spot event usually don't lead to any precursor.
Look to event sequences instead.
Check for sequence of earthquakes, they have to belong to the same fault 
system and/or be focused on a constrained area (which can be also rather 
large, this depends on the seismogenetic structures).

Usually dangerous eq sequences follows the seismo structure you have.
Check then on the historical records of that area for as back in time 
you can go and try to see time related patterns.

Often the huge ground blocks push to each other and a fault depend on 
the other, for sure you can find lot of literature about it for your area.

Then draw a chart of magnitude of earthquake (Y axis) and time (X axis) 
and see if magnitude and frequency increase or decrease. Pay much 
attention if frequency and magnitude stops suddenly.

If eq sequence go up in frequency and magnitude, stay in alert.
If eq sequence go slowily down in freq. and magnit. probably is only an 
ew swarm that will exaust with no damages.

best regards
Mauro



Il 18/07/2010 23:32, George Bush ha scritto:
> Hello-
>
> This morning we had a M2.8 quake about 4 miles west of us out in the
> ocean and about 5 miles from the San Andreas fault that runs to the East
> of us. It was on a minor fault that runs parallel to the San Andreas.
> The shock knocked my data acquisition computer off-line, but was strong
> enough to jiggle the pen on my drum recorder that also was off line!
>
> I am wondering if the movement of the minor fault will add strain or
> relieve strain on the San Andreas fault (add or decrease the chances of
> the San Andreas fault letting-go).
>
> I would appreciate any thoughts or opinions on this from you PSN folks.
>
>
> George Bush
> Sea Ranch, CA, USA
> 38.73775N, 123.48882W
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