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┌─────────────────────────────────────────────────────────────────────────────┐
│▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒ California Division of Mines & Geology ONLINE ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒│
└─────────────────────────────────────────────────────────────────────────────┘
October 6, 1994
Weekly Earthquake Report for Southern California
------------------------------------------------
September 29 - October 5, 1994
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 818-395-6326.
For daily updates, call our Earthquake Information Hotline:
818-395-6977.
--------------------------------
This week's Report covers the time period from midnight Thursday
morning, September 29, Pacific Daylight Time, to midnight Wednesday
night, October 5, Pacific Daylight Time. We recorded only 255
earthquakes of M1.0 or larger this week.
The most widely felt event this week occurred just south
of the area shown on the map. It was a M4.6 in northern Baja,
about 55 mi. SSE of Mexicali, at 7:00 am on Tuesday morning.
It was felt as far north as the Imperial Valley and Yuma, Arizona.
This area is the transition between the East Pacific Rise spreading
ridge and the southern end of the San Andreas Fault at the Salton
Sea, and is very active seismically.
The largest event inside our coverage area was a M3.1 in
the Solvang area, early Monday morning. Although it was certainly
large enough to feel, no-one called us about it.
The only quake that was reported felt was a M2.7 Northridge
aftershock on Friday morning.
Notice the low number of events this week. Although,
statistically, the number of quakes varies from week to week,
a slow overall decline is apparent with the decline of the two
major aftershock sequences (Landers/Big Bear and Northridge).
For statistics buffs, we present a summary of the events processed
so far from these sequences (through September 30):
Northridge
----------
All events 10,314+
3.0 - 3.9 409
4.0 - 4.9 49
5.0 and up 9
GMT date GMT time Latitude Longitude Depth Mag
1994 1 17 12 30 55.39 34 12.80 -118 32.22 18.40 6.7
1994 1 17 12 31 57.82 34 16.76 -118 28.43 0.00 5.9
1994 1 17 12 40 35.71 34 20.49 -118 36.10 0.01 5.2
1994 1 17 23 33 30.69 34 19.58 -118 41.90 9.83 5.6
1994 1 18 0 43 8.89 34 22.59 -118 41.89 11.34 5.2
1994 1 19 21 9 28.61 34 22.71 -118 42.64 14.44 5.1
1994 1 19 21 11 44.90 34 22.65 -118 37.06 11.33 5.1
1994 1 29 11 20 35.95 34 18.32 -118 34.76 1.04 5.1
1994 3 20 21 20 12.26 34 13.88 -118 28.50 13.09 5.3
We are almost, but not quite, finished with the preliminary
data processing of the Northridge sequence.
Landers/Big Bear
----------------
All events 44,117+
3.0 - 3.9 1,462
4.0 - 4.9 157
5.0 and up 21
GMT date GMT time Latitude Longitude Depth Mag
1992 4 23 4 50 23.22 33 57.67 -116 19.05 12.38 6.1
1992 5 18 15 44 17.97 33 57.06 -116 20.25 6.57 5.0
1992 6 28 11 57 34.13 34 12.03 -116 26.14 1.03 7.3
1992 6 28 12 0 45.00 34 7.84 -116 24.49 0.01 5.6
1992 6 28 12 1 16.19 34 7.19 -116 19.39 6.00 5.4
1992 6 28 12 36 40.64 34 8.09 -116 26.06 7.39 5.3
1992 6 28 12 40 53.82 34 19.83 -116 32.84 6.00 5.4
1992 6 28 14 43 21.85 34 9.71 -116 51.13 11.06 5.5
1992 6 28 15 5 30.73 34 12.16 -116 49.61 5.32 6.2
1992 6 28 17 1 31.92 34 10.71 -116 55.35 13.72 5.1
1992 6 28 17 5 57.56 34 15.31 -116 54.72 7.66 5.0
1992 6 29 14 8 37.73 34 6.27 -116 24.19 10.35 5.5
1992 6 29 14 13 38.78 34 6.49 -116 24.23 9.88 5.0
1992 7 1 7 40 29.90 34 19.84 -116 27.76 8.28 5.3
1992 7 5 21 18 27.14 34 34.95 -116 19.07 0.11 5.4
1992 8 17 20 41 52.12 34 11.70 -116 51.76 11.27 5.0
1992 9 15 8 47 11.29 34 3.82 -116 21.64 8.30 5.1
1992 11 27 16 0 57.49 34 20.40 -116 54.00 1.44 5.4
1992 12 4 2 8 57.50 34 22.12 -116 53.88 2.97 5.2
1993 8 21 1 46 38.40 34 1.76 -116 19.27 9.05 5.0
1994 6 16 16 24 27.52 34 16.07 -116 24.09 3.43 5.0
The total numbers of quakes in our area are:
1990 10,738
1991 9,355
1992 50,672+
1993 20,190
1994 22,217 so far
The years prior to 1990 had similar numbers to 1990, about 10,000
per year. The increase in the past 3 years has been due
exclusively to the aftershocks of Landers/Big Bear and Northridge.
The plus sign means that we aren't finished with that part of
the Landers sequence, and there are likely to have been more quakes
than the estimate given.
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 Daylight
Time listed.
Table 1
-------
Date Time N Lat. W Long. Mag
-------------------------------------------------------------
9/29 12:21 am 36 46.0 118 11.6 2.3 2 mi. S of Independence
9/29 1:05 am 34 14.4 118 34.7 2.5 2 mi. W of Northridge
9/29 1:27 am 33 59.6 116 16.3 2.4 13 mi. SE of Yucca Valley
9/29 5:07 am 34 47.2 116 18.0 2.5 35 mi. SSW of Baker
9/29 9:30 am 34 47.0 116 18.1 2.0 "
9/29 12:26 pm 34 21.5 118 39.1 2.1 5 mi. SW of Magic Mtn.
9/29 2:26 pm 32 57.4 117 39.1 2.0 22 mi. SW of Oceanside
9/29 8:33 pm 34 34.5 116 37.1 2.0 20 mi. ENE of Lucerne Valley
9/29 11:44 pm 34 46.5 116 17.5 2.1 36 mi. SSW of Baker
9/30 2:24 am 34 21.4 116 28.5 2.0 16 mi. N of Yucca Valley
9/30 10:22 am 34 16.8 118 30.5 2.7 3 mi. NNE of Northridge; FELT
9/30 5:05 pm 34 48.7 120 58.3 2.2 24 mi. NW of Pt. Arguello
9/30 6:09 pm 34 46.6 117 13.6 2.1 13 mi. SW of Barstow
9/30 7:42 pm 35 3.2 116 59.3 2.6 11 mi. N of Barstow
10/1 9:41 am 34 47.4 116 18.3 2.4 35 mi. SSW of Baker
10/1 10:15 am 33 14.7 115 37.4 2.0 Obsidian Butte area, 6 mi.
W of Niland
10/1 1:58 pm 34 22.1 118 36.3 2.3 3 mi. SSW of Magic Mtn.
10/1 5:02 pm 33 59.9 116 34.5 2.0 4 mi. WNW of Desert Hot
Springs
10/1 6:54 pm 34 2.5 117 31.1 2.1 Fontana, 2 mi. SE of the
I10/I15 interchange
10/2 3:56 am 34 9.0 116 25.4 2.1 2 mi. NNE of Yucca Valley
10/2 8:19 am 34 12.1 116 49.6 2.7 4 mi. SSE of Big Bear City
10/2 6:09 pm 35 1.4 116 58.5 2.2 9 mi. NNE of Barstow
10/2 6:19 pm 35 1.3 116 58.5 2.3 "
10/2 8:25 pm 34 21.1 118 33.5 2.3 2 mi. SW of Newhall
10/3 1:28 am 34 34.1 120 3.1 3.1 5 mi. ESE of Solvang
10/3 5:34 am 34 36.8 116 38.5 2.3 20 mi. NE of Lucerne Valley
10/3 10:14 am 33 41.8 120 6.9 2.1 17 mi. S of Santa Rosa Is.
10/3 4:50 pm 35 44.7 118 0.6 2.3 20 mi. S of Coso Junction
10/3 5:25 pm 33 11.7 115 34.1 2.8 Obsidian Butte area, 4 mi.
SW of Niland
10/3 11:06 pm 34 15.7 116 35.5 2.0 12 mi. NW of Yucca Valley
10/4 3:31 am 33 47.7 117 38.7 2.0 7 mi. SW of Corona
10/4 7:22 am 34 21.0 118 33.5 2.4 2 mi. SW of Newhall
10/4 11:29 am 33 54.1 118 33.4 2.2 Offshore, 7 mi. WSW of Los
Angeles Airport
10/4 1:39 pm 34 33.4 116 24.5 2.1 30 mi. N of Yucca Valley
10/4 2:37 pm 34 30.6 116 31.3 2.0 27 mi. N of Yucca Valley
10/4 3:54 pm 34 22.2 116 27.3 2.1 17 mi. N of Yucca Valley
10/4 6:45 pm 34 24.2 116 28.3 2.0 19 mi. N of Yucca Valley
10/4 7:57 pm 32 55.4 116 20.5 2.2 18 mi. SE of Julian
10/5 4:16 am 34 19.3 118 32.7 2.1 4 mi. SSW of Newhall
10/5 5:03 am 35 21.4 118 34.2 2.1 17 mi. NNW of Tehachapi
10/5 11:22 pm 36 46.0 118 12.0 2.4 2 mi. S of Independence
-------------------------------------------------------------
Figure 1. A map of southern California showing the earthquakes
recorded during the past week by the Caltech/USGS Seismic
Network. Major faults are marked, as well as the metropolitan
areas of Los Angeles (L.A.), Palm Springs (P.S.), San Diego
(S.D.), and Santa Barbara (S.B.). The circles denote the
earthquakes, the size of the circle indicating the magnitude.
-------------------------------------------------------------
CDMG ONLINE
California Division of Mines and Geology
Computer Bulletin Board System
══════════════════════════[ (916) 327-1208 8 - N - 1 ]════════════════════════