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Re: 7.0 Landers Aftershock

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For what it's worth--Caltech is reporting this as a new earthquake.  It is on
the east edge of the Landers aftershock zone and that is where the confusion
came in.  In the Landers area there are a number of parallel faults.  This event
occurred on one of the faults to the east where several aftershocks from Landers
had been recorded.  This is not an aftershock--it is a new event.  This raises
many questions as to the impact on the San Andreas Fault.  Landers raised the
probabilities in some areas and lowered the probabilities in others.  It will
take some time to figure out the impacts.  USGS will publish a report, at
sometime in the future, as to the anticipated impacts on both the San Andreas
and the San Jacinto Faults.

Hope this clears up the confusion.

Greg Smith wrote:

>      Why is this being called an aftershock?  It seems that an earthquake
> has occured.  Hope everyone's OK.
> Greg
> -----Original Message-----
> From: Roger Turk <73527.1356(--nospam--at)>
> To: seaint(--nospam--at) <seaint(--nospam--at)>
> Date: Saturday, October 16, 1999 1:34 PM
> Subject: RE: 7.0 Landers Aftershock
> >Paul,
> >
> >After this quake and the previous Landers EQ that caused buildings in
> Phoenix
> >to sway and creak and caused the strong motion instrument at the Palo Verde
> >Nuclear Generating Plant to trigger, don't you think that it is time to
> >eliminate Seismic Zone 1 from *all* parts of Arizona?  Paul, can you check
> >with the VA Hospital in Phoenix to see if their strong motion instrument
> >triggered?  You may have to do some digging to find someone that knows that
> >they have one.  (Is there someone from Menlo Park on the list that could
> >answer this question?)
> >
> >While the EQ physically woke you and your wife up (and prompted a very
> >germane question from her), I would hope that it also woke up all
> Structural
> >Engineers in Arizona to the absurdity of having Seismic Zone 1 in Arizona.
> >
> >It is well known that there is a geologic "duct" that causes earthquakes
> east
> >of the coast mountains in California to be felt in Phoenix, but not so
> >readily in Tucson.  (A similar geologic "duct" exists between Nevada and a
> >remote area in Siberia in the former USSR, which is where the Russians
> >constructed a seismic station to monitor nuclear tests in the Nevada
> >desert.)  While Tucson is not so susceptible to California earthquakes,
> >faults in southern Arizona and northern Mexico, namely the Piticachi (sp?)
> >fault have caused problems in southeastern Arizona.
> >
> >A. Roger Turk, P.E.(Structural)
> >Tucson, Arizona
> >
> >Paul Blomberg wrote:
> >
> >. > The quake woke me up this morning in Phoenix, AZ.  My  wife wanted to
> know
> >. > if our house was designed good enough for earthquakes.
> >. >
> >. > Paul F. Blomberg
> >