December 29, 1994 Weekly Earthquake Report for Southern California ------------------------------------------------ December 22 - 29, 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, December 22, Pacific Standard Time, to midnight Wednesday night, December 29, Pacific Standard Time. We recorded 355 earth- quakes of M1.0 or larger during the 7-day period covered. Southern California had a relatively peaceful holiday, seismically speaking. No events were felt, or at least no-one was sufficiently concerned to call us. There were two small swarms in evidence: one in the Coso Range east of Haiwee Reservoir and the other under the Salton Sea, a few miles south of Bombay Beach. The week's largest event, M3.4 just before midnight on Christmas Eve, was a member of the Coso swarm. Both of these sites have experienced many similar swarms in the past. The Coso region had a particularly large number of earthquakes in the early 1980's, with the largest event in 1982 being M4.9. The site in the Salton Sea is near the northern end of the Brawley Seismic Zone, which is known for it's swarm activity. There was also a M3+ quake on Wednesday in the Coalinga area; readers are referred to Menlo Park's report for details. Please have a happy New Year. 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 ------- Date Time N Lat. W Long. Mag ------------------------------------------------------------- 12/22 3:19 am 34 24.9 116 29.8 2.2 20 mi. N of Yucca Valley 12/22 5:19 am 33 17.2 115 42.2 2.8 4 mi. SSE of Bombay Beach 12/22 6:29 am 34 28.4 116 30.1 2.5 24 mi. N of Yucca Valley 12/22 7:23 am 33 16.4 115 42.5 2.1 4 mi. SSE of Bombay Beach 12/22 7:48 am 33 17.1 115 42.0 2.7 " 12/22 8:01 am 33 17.2 115 42.1 2.0 " 12/22 8:03 am 33 17.1 115 42.2 2.6 " 12/22 12:01 pm 34 9.6 116 25.5 2.1 3 mi. NNE of Yucca Valley 12/23 6:25 am 36 7.0 117 50.7 2.1 5 mi. ESE of Haiwee Reservoir 12/23 7:54 am 36 7.0 117 50.4 2.1 " 12/23 12:57 pm 34 47.5 116 17.7 2.9 35 mi. SSW of Baker 12/23 1:12 pm 34 47.4 116 17.7 2.8 " 12/23 2:09 pm 36 7.2 117 50.3 2.3 5 mi. ESE of Haiwee Reservoir 12/23 9:02 pm 34 5.7 116 24.6 2.5 2 mi. SE of Yucca Valley 12/24 1:33 am 33 29.4 116 45.9 2.6 7 mi. SW of Anza 12/24 1:46 am 34 9.8 116 24.8 2.4 3 mi. NNE of Yucca Valley 12/24 2:04 am 32 59.5 115 34.9 2.0 3 mi. NW of Brawley 12/24 3:01 am 35 56.8 118 12.2 2.0 15 mi. WSW of Coso Junction 12/24 5:48 am 34 38.5 118 35.2 2.0 8 mi. N of Castaic Lake dam 12/24 8:00 am 36 7.0 117 50.3 2.1 6 mi. ESE of Haiwee Reservoir 12/24 9:43 am 34 18.0 118 27.3 2.0 1 mi. NW of San Fernando 12/24 6:59 pm 34 47.2 116 17.6 2.4 35 mi. SSW of Baker 12/24 7:51 pm 33 14.6 116 6.4 2.2 7 mi. NNE of Ocotillo Wells 12/24 10:11 pm 36 6.8 117 50.2 2.2 6 mi. ESE of Haiwee Reservoir 12/24 11:59 pm 36 6.8 117 50.4 3.4 " 12/25 2:15 am 36 7.0 117 50.5 2.4 " 12/25 3:58 am 36 7.1 117 50.2 2.4 " 12/25 3:59 am 36 6.9 117 50.5 2.7 " 12/25 4:53 am 33 43.6 118 3.0 2.0 3 mi. ESE of Seal Beach 12/25 8:20 am 34 29.1 116 29.7 2.0 25 mi. N of Yucca Valley 12/25 10:37 am 34 17.6 118 39.3 2.2 3 mi. ENE of Simi Valley 12/25 2:28 pm 36 7.6 117 50.5 2.0 5 mi. E of Haiwee Reservoir 12/25 11:06 pm 33 14.5 116 6.3 2.3 6 mi. NNE of Ocotillo Wells 12/25 11:50 pm 34 34.5 116 32.5 2.6 24 mi. ENE of Lucerne Valley 12/26 5:17 am 36 7.4 117 49.9 2.1 6 mi. E of Haiwee Reservoir 12/26 4:45 pm 36 7.7 117 50.2 2.7 " 12/27 2:59 am 36 7.0 117 50.0 2.0 " 12/27 5:21 am 36 6.8 117 50.4 2.0 " 12/27 5:42 am 34 24.0 116 28.2 2.6 19 mi. N of Yucca Valley 12/27 11:04 am 34 29.1 116 30.9 2.4 25 mi. N of Yucca Valley 12/27 2:43 pm 35 2.1 116 59.9 2.5 10 mi. N of Barstow 12/27 4:01 pm 32 47.6 118 19.4 2.0 2 mi. SE of San Clemente Is. 12/28 4:49 am 36 18.4 120 22.2 3.3 11 mi. N of Coalinga 12/28 6:04 am 36 0.6 117 49.1 2.4 7 mi. ESE of Coso Junction 12/28 4:40 pm 34 12.9 118 30.7 2.1 1 mi. SE of Northridge 12/28 5:14 pm 34 23.3 116 27.4 2.2 18 mi. N of Yucca Valley 12/28 7:51 pm 34 27.8 119 21.8 2.1 6 mi. W of Ojai 12/28 10:15 pm 34 27.9 119 21.9 2.1 " ------------------------------------------------------------- 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.