From: bverreau@netcom.COM (stargazer)
Subject: Re: The Next Big Quake (Was: Moving to San Mateo, but where?)
Date: Fri, 04 Sep 92 19:27:52 GMT
Organization: Armchair Seismologists
Summary: East Bay's turn
Reply-To: bverreau@netcom.COM (stargazer)
Distribution: ca

In article <1992Sep3.174416.24216> dave@berlioz.nsc.com (David Hawley) writes:

>(2) There was a list of earthquakes of magnitude 6 or greater in the
>    Bay Area.  Can someone fill in the locations?

I don't know how closely this corresponds to your list, but here's a
list I posted a few years ago pursuant to a discussion of "paired"
earthquakes in the Bay Area.

> In article <816@helens.Stanford.EDU> (Joe Dellinger) writes:
>
>> In article <37681@ucbvax.BERKELEY.EDU> (ethan miller) writes:
>>> Does anyone know anything about "twin quakes?"
>> Last century, when the Bay Area apparently had more frequent large quakes
>> than it has since 1906, the quakes did seem to come in groups.
>
> I thought it might be interesting to see if the data bore this out,
> so I tracked down some references to historic Bay Area earthquakes.
> My sources are "Earthquake Planning Scenario Special Publication 78",
> Divisions of Mines and Geology (1987); "Probabilistic Long-Term Fore-
> casts of Major Earthquakes in the San Francisco Bay Region", the Bay
> Area Earthquake Study (1984); "Peace of Mind in Earthquake Country",
> Peter Yanev (1974).  Events in the following table are grouped where
> separated by fewer than five years.  Some entries are combined data.
>
> DATE             LOCALITY/FAULT               M (estimated)    MM
> ----             --------------               -------------    --
> June 1808        San Francisco/San Andreas                     VIII
>
> June 10, 1836    Oakland/Hayward              6.8              IX-X
> June 1838        Woodside/San Andreas         7.0              X
>
> Nov. 26, 1858    San Jose/Hayward             6.1              VIII
> July 3, 1861     Livermore/Calaveras                           VIII
> Feb. 26, 1864    Gilroy/San Andreas           5.9              VI
> Oct. 8, 1865     Santa Cruz/San Andreas       6.3              VIII
> Oct. 1, 1868    *Eureka/San Andreas                            VIII-IX
> Oct. 21, 1868    San Leandro/Hayward          6.8              IX-X
>
> April 19, 1892  *Vacaville/?                                   IX
> April 21, 1892   Winters/Antioch              6.4              IX
>
> June 20, 1897    Hollister/Hayward                             VIII
> March 31, 1898   Sonoma/Rodgers Creek         6.2              VIII
>
> April 18, 1906  *Brawley/Imperial             6-6.9            VIII
> April 18, 1906   San Francisco/San Andreas    7.8              XI
>
> July 1, 1911     Coyote/Calaveras             6.6
>
> Oct. 22, 1926    Monterey Bay/San Gregorio    6-6.9            VIII
>
> April 24, 1984   Morgan Hill/Calaveras        6.2
>
>               (*) not in Bay Area, but perhaps related?
>
> There does seem to be some clustering, particularly in the decade
> from 1858-1868.  All major quakes since 1906 have been "loners".
> The last Santa Cruz Mt. quake (1868) was followed three years
> later by a major tremor on the Hayward.  Perhaps someone with
> some math background would care to do a statistical analysis?
>
>> Certainly this isn't a well established theory...
>
> Too few data points.

I believe someone posted a followup in which they presented an analysis
of this data which indicated a a non-random distribution of earthquakes
over time.

Bernie Verreau						bverreau@netcom.COM
Netcom - Online Communication Services 			Redwood City, CA