From: andy@pangea.Stanford.EDU (Andy Michael USGS Guest)
Subject: Re: The Next Big Quake (Was: Moving to San Mateo, but where?)
Organization: Stanford Univ. Earth Sciences
Distribution: ca
Date: Thu, 3 Sep 1992 19:04:49 GMT

In article <1992Sep3.174416.24216@berlioz.nsc.com> dave@berlioz.nsc.com (David Hawley) writes:
>After the Loma Prieta earthquake, the USGS created a publication which
>was distributed free in the local newspapers called, "The Next Big
>Earthquake (in the Bay Area may come sooner than you think)".  At the
>time, copies were available by writing to Earthquakes, USGS,
>345 Middlefield Rd., Menlo Park, CA 94025.  If they're still available,
>they would be an excellent first reference for new arrivals worried
>about earthquakes.  Here are the table of contents:
Currently we are out of copies unless you can talk someone out of one they
have stockpiled.  Hard work is going into getting them reprinted and in
changing some of the financial policies that make it hard for the group
that has a "bestseller."

>I happened to find my copy recently, and had a few questions:
>
>(1) Has a similar publication been created for Southern California?
No, not yet anyway.  If you think one should lobby the group at Caltech
or the USGS office in Pasadena.

>(2) There was a list of earthquakes of magnitude 6 or greater in the
>    Bay Area.  Can someone fill in the locations?
See, USGS Professional Paper 1515, The San Andreas Fault System,
California.  (Gee I wonder how many times I'll get to reccommend that
wonderful book).

>The gap between 1911 and 1979 is really amazing!  It appears we are
>starting on another sequence of "normal" activity.  The reason I'm
>interested in the locations is that is seems that major quakes in the
>bay area are preceeded by activity on adjacent faults.  For example,
>in the 10 years before Loma Prieta, a series of quakes moved up the
>Calaveras Fault from Hollister to San Jose (east of the San Andreas),
>then Los Gatos (just north of LP) got a couple of significant quakes
>(5.0 in June 88, 5.2 in Aug 89).  Are there other examples of this,
>where smaller quakes form a pattern pointing to a later larger one, over
>several years?  How about in Southern California, where the situation
>is a lot more complex?  Any recent research or developments?
There have been some papers on this topic by Sykes and Jaume in Nature
I think.  And Bill Ellsworth wrote a paper on the topic that is in the 
American Geophysical Union Ewing Series Volume 4 "Earthquake Prediction
An International Review" published in 1981.  It is certainly a hot topic.
The basic idea that most people would agree on is that 1906 removed so
much stress from the region due to its large amount of slip and large
fault length that the other faults were moved away from the failure
level.  Bob Simpson has done some physical modelling of this but I am
not sure if it has been published yet.

>(3) Unrelated, but what ever happened to the "Palmdale Bulge"?
Most common explanation was that the bulge never existed, it just
appeared to because of a failure to properly correct for refraction in
the atmosphere when reducing the surveying data.  This can happen
because the refraction is dependent on atmospheric conditions.  The
Landers quake was in the suppossed bulge and someone put a map on the
bulletin board here pointing that out.  Soon after someone wrote a note
on it saying, "The first earthquake predicted by atmospheric refraction!"

Andy