SOUTHERN CALIFORNIA
SEISMOGRAPHIC NETWORK
A Cooperative Project of
Caltech and the U.S. Geological Survey
July 6, 1995
Weekly Earthquake Report for Southern California
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June 29 - July 5, 1995
Prepared by: Kate Hutton, Seismological Laboratory
(kate@bombay.gps.caltech.edu)
Lucy Jones, U.S. Geological Survey
California Institute of Technology
For further information, please contact the authors or the
Caltech Public Relations Office at 818-395-6326. For daily
updates, call our Earthquake Information Hotline: 818-395-6977.
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This week's Report covers the time period from midnight Thursday
morning, June 29, Pacific Daylight Time, to midnight
Wednesday night, July 5, 1995, Pacific Daylight Time. We
recorded 287 earthquakes of M1.0 or larger during the 7-day
period covered.
We were back to relative peace this week; there were no
quakes above M3 in our region. In fact, the only quake that
was reported as felt was a M2.4 (Landers aftershock) near Yucca
Valley yesterday afternoon. The week's largest quake was a M2.9
in the Saline Valley area, northeast of Lone Pine.
The L.A. Basin continued it's normal level of activity,
which included three small events near the northern Newport-
Inglewood fault zone, the largest of which was M2.1.
The end of the quarter happened this week, however, so
we have the statistical summary to present. Here are the totals
for the past few years, listed by 3-month period. Two figures
are listed for each quarter: the first is the total number of
earthquakes, and the second is the total M3 or larger.
1st quarter 2nd quarter 3rd quarter 4th quarter
all 3.0+ all 3.0+ all 3.0+ all 3.0+
1990 3,483 56 2,627 45 2,225 27 2,403 31
1991 2,041 11 2,218 32 2,445 23 2,651 29
1992 3,618 40 10,288 744 25,500+ 801 10,700+ 166
1993 4,939 43 5,370 61 5,298 48 4,583 35
1994 10,915 417 5,967 43 5,400 48 5,031 40
1995 3,815 28 3,982 39
The totals for the Northridge sequence, from January
17, 1994 through the end of June 1995, are:
All events 11,866 (446 more this quarter)
3.0 - 3.9 378
4.0 - 4.9 48
5.0 and up 10
That last M5 was, of course, the M5.0 that occurred on June
26, 1995.
Similar totals for the Landers/Big Bear sequence are
as follows:
All events 56,000+ (1,735 more this quarter)
3.0 - 3.9 1,530
4.0 - 4.9 162
5.0 and up 21
The last M5 in the Landers/Big Bear sequence was a M5.0 that
occurred on June 16, 1994. The + sign indicates that we are
not finished with the data processing yet; however, all the
events that are left to process are less than M3.
Notice that this quarter's contribution from the
Landers/Big Bear sequence is significantly larger than the
contribution from the Northridge sequence. This is because of
the larger magnitude of the Landers mainshock, Mw7.3 rather
than Mw6.7. The aftershock sequence from the larger quake is
expected to be much more prolific and last longer than that of
the smaller one.
The table lists the quakes this week that were M2.0 or
larger in the central part of the coverage area. Times are local
times; if you want Greenwich Mean Time, add 7 hrs to the Pacific
Daylight Time or 8 hrs to the Pacific Standard Time listed.
Table 1
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Date Time N Lat. W Long. Mag
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6/29 12:14 am 35 2.1 117 0.2 2.3 10 mi. N of Barstow
6/29 1:27 am 34 7.1 116 52.0 2.2 2 mi. WNW of Mt. San
Gorgonio
6/29 8:39 am 33 16.6 115 39.0 2.5 6 mi. SE of Bombay Beach
6/29 9:56 am 32 59.4 117 49.1 2.5 32 mi. SSW of San
Clemente
6/29 10:43 am 33 58.5 117 2.8 2.2 5 mi. NW of Beaumont
6/29 2:13 pm 34 16.8 118 30.2 2.2 3 mi. NNE of Northridge
6/29 7:01 pm 34 21.3 116 54.1 2.5 6 mi. SSE of Lucerne
Valley
6/29 10:53 pm 33 40.9 116 43.7 2.2 4 mi. S of Idyllwild
6/29 11:40 pm 34 17.2 118 40.8 2.0 1 mi. ENE of Simi Valley
6/30 4:26 am 34 1.4 118 22.5 2.1 1 mi. N of Baldwin Hills
6/30 1:07 pm 34 20.7 116 28.5 2.0 15 mi. N of Yucca Valley
6/30 1:07 pm 32 52.1 115 56.8 2.1 9 mi. NNE of Ocotillo
6/30 4:28 pm 35 1.4 116 57.7 2.0 10 mi. NNE of Barstow
6/30 6:30 pm 35 2.5 116 59.6 2.3 10 mi. N of Barstow
6/30 8:52 pm 36 0.5 117 48.7 2.3 Coso Range, 7 mi. ESE of
Coso Junction
6/30 8:53 pm 36 0.5 117 48.9 2.2 "
6/30 8:54 pm 36 0.6 117 49.0 2.3 "
7/1 8:24 am 35 18.2 118 29.6 2.2 12 mi. NNW of Tehachapi
7/1 4:04 pm 33 57.6 118 19.2 2.1 1 mi. NE of Hollywood Park
Racetrack
7/2 3:41 am 34 59.2 116 57.0 2.6 7 mi. NNE of Barstow
7/2 5:02 am 34 15.9 117 38.5 2.0 1 mi. SSE of Mt. Baldy
7/2 5:33 pm 34 12.8 116 26.5 2.1 6 mi. N of Yucca Valley
7/2 6:17 pm 33 20.9 116 26.0 2.4 7 mi. NNW of Borrego
Springs
7/2 7:08 pm 35 4.1 116 39.3 2.2 23 mi. SSE of Goldstone
(dry) Lake
7/2 8:02 pm 34 38.3 117 27.1 2.5 11 mi. NW of Victorville
7/2 10:16 pm 36 7.5 117 51.0 2.6 Coso Range, 5 mi. E of
Haiwee Reservoir
7/2 10:21 pm 36 7.4 117 51.1 2.3 "
7/3 3:37 am 34 59.5 116 56.7 2.4 8 mi. NNE of Barstow
7/3 4:42 am 33 31.1 117 39.6 2.3 7 mi. NNW of San Clemente
7/3 11:02 am 32 52.6 117 43.2 2.2 29 mi. SW of Oceanside
7/3 12:58 pm 34 34.0 116 27.8 2.3 31 mi. N of Yucca Valley
7/3 1:53 pm 36 55.0 117 41.2 2.9 30 mi. NE of Lone Pine
7/3 4:11 pm 35 1.9 116 60.0 2.0 9 mi. N of Barstow
7/4 5:28 am 33 26.5 119 4.3 2.0 2 mi. SSW of Santa
Barbara Is.
7/4 12:06 pm 33 12.9 116 4.6 2.5 5 mi. NNE of Ocotillo
Wells
7/4 9:19 pm 34 13.1 117 2.8 2.1 3 mi. ENE of Running
Springs
7/4 11:37 pm 35 0.9 116 57.5 2.6 9 mi. NNE of Barstow
7/5 3:37 am 34 7.0 116 24.4 2.4 2 mi. E of Yucca Valley
FELT
7/5 5:20 am 34 13.6 118 29.6 2.4 2 mi. ESE of Northridge
7/5 6:13 am 33 56.1 116 37.7 2.0 7 mi. WSW of Desert Hot
Springs
7/5 8:23 am 32 18.9 115 16.4 2.8 27 mi. SSE of Calexico
7/5 9:18 pm 33 31.7 117 38.7 2.5 7 mi. NNW of San Clemente
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