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Re[2]: 7.0 Landers Aftershock

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I saw Lucy Jones (USGS Cal Tech) on the news this weekend, and she reported that
this 10/16/99 M 7.0 was not a Landers aftershock.  This is clear now since we
know that the earthquake was the result of strike slip rupture on another fault
to the east (Pisgah), not the Emerson or similar faults.  Basically, the
earthquake was at 29 Palms (MCAGCC), rather than Yucca Valley.  I understand
that they had to stop live fire exercises by the Marines, so geologists could
look for surface rupture.

I'm sorry to say I'm not sure if your comment about "aftershocks" was levity or
not.  But to answer your question, there have been many Landers aftershocks even
this year, month and week, as defined (or reported) by USGS and others.  My
understanding is that an aftershock is simply energy released on the same fault
zone as an earlier earthquake.  Since this was on a different fault to the east,
the earthquake this weekend was not an aftershock.  However, I don't think you
need to be a geophysicist to see that strike slip stress release on the Emerson
and associated faults, could be transferred to the Pisgah and associated faults
that are roughly parallel.  It is interesting to note that there are small
segments of the Pisgah Fault that moved in 1992, as mapped on Jennings 1994
"Fault Activity Map of California."  Other than this map, all my data is from
local (LA) TV, so consider the early source.

Anybody know more about where there was surface rupture, and how much?  I don't
think we can just drive on to 29 Palms MCAGCC to look for rupture.  We would
more likely find unexploded ordnance.

Tom Benson at Lowney Associates, (626) 396-1490  

____________________Reply Separator____________________
Subject:    Re: 7.0 Landers Aftershock 
Author: <seaint(--nospam--at)seaint.org>
Date:       10/18/99 4:04 PM

     Can there REALLY be an aftershock from an EQ that happened in '92?