From    : W6VIO @ W6VIO
To      : QUAKE
Date    : 921216/1409
Msgid   : BN 43193@W6VIO $43193_W6VIO
Subject : S. Cal Weekly Rpt 12/3 - 12/9


[ W6VIO SYSOP NOTE:  Sorry for the delay in posting this report.  Cal Tech
  only released it this morning 12/16/92.  They been rather busy! ]


                                                December 10, 1992

                Weekly Earthquake Report for Southern California
                ------------------------------------------------
                             December 3 - 9, 1992

        Prepared by:  Kate Hutton, Seismological Laboratory
                      (kate@bombay.gps.caltech.edu)
                      Lucy Jones, U.S. Geological Survey
                      California Institute of Technology

        This document is a commentary on current seismic activity.  The
        earthquakes discussed have been detected and processed
        automatically.  All epicenters and magnitudes have been reviewed
        to exclude obvious blunders; however, they must still be
        considered preliminary.  For further information, please contact
        the authors or the Caltech Public Relations Office at (818) 356-6326.

                        --------------------------------

        This week's Report covers the time period from midnight Thursday
        morning, December 3, Pacific Standard Time, to midnight Wednesday
        night, December 9, Pacific Standard Time.  Aftershocks of the
        Landers earthquake continue, as they will for several years at
        least.  The map includes a virtually complete set of earthquakes of
        M2.5 or larger, plus many smaller ones that happen to have made
        it through the data processing.  There are 571 in all.
                The main action this week was another M5+ shock at the
        northern edge of the San Bernardino Mountains.  This one registered
        M5.1, and occurred on Thursday evening.  The focal mechanism showed
        thrust along an ENE trending fault, but no fault has been
        identified as yet, for either this week's or last week's Big Bear
        aftershock.  The M5.1 could be considered a sort of third-level
        nested aftershock.  It was an aftershock of the November 27 M5.4,
        which was an aftershock of the June 28 M6.3 (Big Bear), which was
        an aftershock of the June 28 M7.4 (Landers).  Furthermore, the
        M5.1 had some aftershocks of its own.
                A number of other small shocks were felt this week, some
        of them quite small.  They are listed in the table.  It is quite
        easy for a human at rest near the epicenter to feel a M2.5 to M3.0
        quake.  Although the aftershock sequence is declining more or less
        as expected, the table shows that there were still a substantial
        number of earthquakes in this size range.  In other words, they
        are not news.  However, every time a person makes an inquiry with
        a radio station about whether that 3 am twitch was an earthquake
        or not, a Public Relations staff member and a seismologist are
        awakened.  We would like to humbly suggest that people could wait
        until normal business hours to settle their bets as to whether it
        was or was not an earthquake.
                Due to the high level of activity this week, we are only
        listing quakes of M2.5 and larger in the table.  As usual, times
        are local times; if you want Greenwich Mean Time, add 8 hrs. to
        the Pacific Standard Time listed.

        Table 1
        -------
        Date  Time      N Lat.   W Long.   Mag
        -------------------------------------------------------------
        12/3   6:45 am  34 16.9  116 46.3  2.7  4 mi. ENE of Big Bear City
        12/3  10:41 am  34 15.3  116 26.0  2.7  9 mi. N of Yucca Valley
        12/3   1:58 pm  34 19.9  116 54.7  2.9  5 mi. NW of Big Bear City
        12/3   3:12 pm  34 20.1  116 54.0  2.5  5 mi. NNW of Big Bear City
        12/3   3:36 pm  34 15.1  116 25.8  2.8  9 mi. N of Yucca Valley
        12/3   5:11 pm  34 20.1  116 54.1  2.7  5 mi. NNW of Big Bear City
        12/3   6:08 pm  34 22.1  116 53.8  5.1  5 mi. SSE of Lucerne Valley
                                                Widely felt.
        12/3   6:13 pm  34 21.7  116 54.0  3.3          "
        12/3   6:13 pm  34 21.5  116 55.3  3.2          "
        12/3   6:15 pm  34 21.8  116 54.6  2.6          "
        12/3   6:19 pm  34 22.3  116 55.0  3.0          "
        12/3   6:34 pm  33 33.1  116 31.8  2.6  8 mi. E of Anza
        12/3   7:12 pm  34 21.5  116 54.7  2.9  5 mi. SSE of Lucerne Valley
        12/3   7:14 pm  34 21.8  116 55.4  3.1          "
        12/3   7:25 pm  34 22.3  116 54.4  3.1          "
        12/3   8:29 pm  34 21.3  116 54.5  2.7          "
        12/3   8:35 pm  34 21.3  116 53.8  2.7  6 mi. NNW of Big Bear City
        12/3   8:38 pm  34 58.1  116 56.3  2.6  7 mi. NE of Barstow
        12/3   8:53 pm  34 22.0  116 54.8  2.5  5 mi. SSE of Lucerne Valley
        12/3   9:25 pm  34 22.6  116 55.1  4.5          "
                                                Felt.
        12/3   9:55 pm  34 21.7  116 55.2  3.0          "
        12/3  11:22 pm  35 50.1  116 37.2  2.5  21 mi. WSW of Shoshone
        12/3  11:33 pm  34 21.6  116 55.5  2.8  5 mi. SSE of Lucerne Valley
        12/4   3:02 am  34 21.8  116 55.6  2.6          "
        12/4   3:07 am  34 38.1  116 30.4  2.5  28 mi. ENE of Lucerne Valley
        12/4   4:59 am  34 21.7  116 54.8  4.0  5 mi. SSE of Lucerne Valley
                                                Felt
        12/4   8:20 am  34 21.8  116 55.3  2.9          "
        12/4  10:00 am  34 22.7  116 55.7  2.9          "
        12/4  10:46 am  35 31.5  117 25.8  2.5  17 mi. SSW of Trona
        12/4  12:51 pm  34  6.8  116 59.6  2.7  8 mi. SE of Running Springs
        12/4   1:52 pm  34 21.0  116 53.2  2.5  6 mi. NNW of Big Bear City
        12/4   2:09 pm  35 22.2  118 37.8  2.5  15 mi. NE of Arvin
        12/4   3:59 pm  34 21.3  116 53.8  2.6  6 mi. SSE of Lucerne Valley
        12/4   8:57 pm  34 21.9  116 55.6  2.7  5 mi. SSE of Lucerne Valley
        12/4   9:20 pm  34 21.8  116 55.3  3.2          "
        12/4  10:14 pm  34 21.8  116 55.3  2.9          "
        12/5  10:08 am  34 20.9  116 52.9  2.6  5 mi. NNW of Big Bear City
        12/5  10:28 am  35  3.6  116 59.4  3.2  11 mi. N of Barstow
                                                Felt.
        12/5  10:42 am  34  0.7  116 18.7  2.6  10 mi. SE of Yucca Valley
        12/5   1:30 pm  34 21.9  116 55.4  2.7  5 mi. SSE of Lucerne Valley
        12/5   2:04 pm  34 21.5  116 54.3  2.5          "
        12/5   6:40 pm  34  8.9  116 25.6  3.1  2 mi. NNE of Yucca Valley
                                                Felt.
        12/5   7:39 pm  34 21.1  116 53.1  2.6  6 mi. NNW of Big Bear City
        12/5   9:59 pm  34 22.0  116 52.9  2.5  6 mi. SE of Lucerne Valley
        12/6   1:34 am  36 26.2  120  3.9  2.5  25 mi. SW of downtown Fresno
        12/6  10:42 am  34 56.4  116 47.3  2.5  13 mi. ENE of Barstow
        12/6   2:35 pm  34 21.2  116 53.8  2.6  6 mi. NNW of Big Bear City
        12/6   4:17 pm  34 36.5  116 38.6  2.5  20 mi. ENE of Lucerne Valley
        12/6   4:49 pm  34 22.6  116 54.0  3.2  5 mi. SSE of Lucerne Valley
                                                Felt.
        12/6   7:31 pm  34 21.8  116 55.7  3.1          "
                                                Felt.
        12/6   7:33 pm  34 21.7  116 55.4  3.9          "
                                                Felt.
        12/6   8:19 pm  34 16.8  116 41.8  2.6  8 mi. E of Big Bear City
        12/6   8:42 pm  34 21.4  116 55.5  2.7  6 mi. S of Lucerne Valley
        12/6  11:25 pm  34 25.3  116 42.2  2.6  13 mi. NE of Big Bear City
        12/6  11:50 pm  35  4.1  116 59.5  3.7  12 mi. N of Barstow
        12/6  11:58 pm  34 21.7  116 55.0  3.0  5 mi. SSE of Lucerne Valley
        12/7   6:41 am  33 32.1  118 24.4  2.8  13 mi. SSW of Pt. Fermin,
                                                San Pedro
        12/7   9:03 am  34 23.1  116 27.7  2.6  18 mi. N of Yucca Valley
        12/7   9:17 am  34 22.4  116 53.6  2.6  5 mi. SSE of Lucerne Valley
        12/7  10:07 am  34 22.9  116 27.7  2.5  18 mi. N of Yucca Valley
        12/7   2:52 pm  35 14.7  118 36.4  2.7  11 mi. NW of Tehachapi
        12/7   4:14 pm  33 58.0  116 18.0  2.9  11 mi. E of Desert Hot
                                                Springs
        12/7  11:52 pm  33 57.8  117 49.4  2.7  5 mi. N of Yorba Linda
        12/8   4:30 am  34 59.8  116 57.0  2.8  8 mi. NNE of Barstow
        12/8  10:42 am  34 22.4  116 52.8  2.6  6 mi. SE of Lucerne Valley
        12/8  11:00 am  35 35.9  118 19.1  2.5  8 mi. ESE of the town of
                                                Lake Isabella
        12/8  11:13 am  35 45.9  120 14.8  2.5  4 mi. NE of Cholame
        12/8  12:06 pm  34 30.9  116 32.0  3.0  25 mi. NE of Big Bear City
        12/8   7:39 pm  34 21.2  116 54.2  3.2  6 mi. SSE of Lucerne Valley
                                                Felt.
        12/8  10:40 pm  34 22.4  116 52.8  2.7          "
        12/8  10:53 pm  34 22.3  116 52.8  2.6          "
        12/9  12:38 am  34 22.0  116 53.6  2.6          "
        12/9   1:23 am  34 21.9  116 53.7  2.6          "
        12/9   1:28 am  34 14.6  116 25.6  3.0  8 mi. N of Yucca Valley
                                                Felt.
        12/9  10:41 am  34 55.0  116 49.3  2.5  11 mi. E of Barstow
        12/9  10:55 am  34 33.6  116 31.0  2.6  25 mi. ENE of Lucerne Valley
        12/9  10:57 am  34 18.5  116 25.9  2.5  13 mi. N of Yucca Valley
        12/9  11:16 am  34 18.7  116 25.6  2.9          "
        12/9  11:47 am  34 18.6  116 25.9  3.2          "
        12/9   1:02 pm  34 56.9  116 55.1  2.5  7 mi. NE of Barstow
        12/9   4:02 pm  34 34.0  116 33.2  3.0  23 mi. ENE of Lucerne Valley
        12/9   5:03 pm  35 44.3  116 32.5  3.2  22 mi. SW of Shoshone
        12/9   5:06 pm  35 43.6  116 33.3  2.7          "
        12/9   6:26 pm  34 58.3  116 56.0  3.4  7 mi. NE of Barstow

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