SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey April 25, 1996 Weekly Earthquake Report for Southern California ------------------------------------------------ April 18 - 24, 1996 Prepared by: Debbie Wells, Seismological Laboratory Nick Scheckel, 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. -------------------------------- This week's Report covers the time period from midnight Thursday morning, April 18, Universal Time (ie. GMT), to midnight Wednesday night, April 24, Universal Time. In local time, the period of coverage is from 5 p.m., April 17, Pacific Daylight Time, to 5 p.m., April 24, Pacific Daylight Time. We detected and processed 341 earthquakes during the 7-day period covered. It was another quiet week. The only notable activity occurred on Friday, in the early afternoon. There was a M3.1 quake near Mt. San Gorgonio, an aftershock of the Landers and Big Bear earthquakes (June 28, 1992, Mw7.3 and Mw6.4), and a M3.1 located 14 miles north of the Salton Sea. Both of these quakes generated some media inquiries, but we received no felt reports. The San Gorgonio earthquake occurred at 11 kilometers depth with a focal mechanism showing a east-striking thrust fault. Thrust faulting is common in the San Bernardino Mountains. The focal mechanism for the earthquake north of the Salton Sea showed normal faulting on a northeast-striking fault. This also is a common focal mechanism for its location. This area northeast of the San Andreas fault is cut by many north-striking strike-slip faults and northeast-striking normal faults. 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 ------------------------------------------------------------- 4/17 5:08 pm 34 37.2 116 33.8 2.0 24 mi. ENE of Lucerne Valley 4/17 9:49 pm 33 35.3 116 38.5 2.0 2 mi. NE of Anza 4/18 12:20 am 33 11.8 115 36.0 2.2 2 mi. NE of Obsidian Butte 4/18 4:03 am 34 22.5 118 48.3 2.0 6 mi. ESE of Fillmore 4/18 11:44 am 33 56.3 116 18.8 2.0 10 mi. E of Desert Hot Springs 4/18 1:31 pm 33 57.5 116 19.6 2.0 " 4/18 7:05 pm 35 5.6 118 18.8 2.0 7 mi. ESE of Tehachapi 4/18 10:44 pm 33 2.3 118 9.7 2.0 18 mi. NE of San Clemente Is. 4/19 4:27 am 36 1.3 119 36.8 2.6 27 mi. SW of Visalia 4/19 10:22 am 34 29.7 116 29.7 2.1 26 mi. N of Yucca Valley 4/19 11:34 am 35 44.0 117 37.0 2.0 8 mi. NNE of Ridgecrest 4/19 12:18 pm 34 8.1 116 51.3 3.1 2 mi. NNW of Mt. San Gorgonio 4/19 12:52 pm 33 44.0 115 55.1 3.1 14 mi. N of North Shore 4/19 5:39 pm 35 44.5 117 38.4 2.3 8 mi. N of Ridgecrest 4/19 9:55 pm 36 7.1 119 52.1 2.2 27 mi. E of Coalinga 4/20 12:03 am 35 44.6 117 38.5 2.0 8 mi. N of Ridgecrest 4/20 2:49 am 34 1.3 117 8.8 2.0 2 mi. SE of Redlands 4/20 5:10 am 34 58.4 116 56.9 2.1 7 mi. NE of Barstow 4/20 12:26 pm 34 28.5 116 30.3 2.0 24 mi. N of Yucca Valley 4/20 4:51 pm 35 29.6 119 20.8 2.0 21 mi. WNW of Bakersfield 4/20 8:03 pm 34 4.9 116 52.9 2.1 3 mi. WSW of Mt. San Gorgonio 4/21 3:21 am 33 20.5 117 52.0 2.2 12 mi. SW of Dana Point 4/21 3:36 am 34 12.7 118 32.0 2.2 Under Reseda 4/21 4:33 am 34 5.1 116 53.0 2.4 3 mi. WSW of Mt. San Gorgonio 4/21 5:47 am 33 58.9 116 46.1 2.2 4 mi. NNE of Cabazon 4/21 10:38 am 33 41.3 116 48.3 2.0 6 mi. SW of Idyllwild 4/22 4:53 am 34 18.1 116 27.2 2.4 12 mi. N of Yucca Valley 4/22 6:27 am 34 24.0 116 28.2 2.1 19 mi. N of Yucca Valley 4/22 7:24 am 35 20.9 118 36.3 2.1 15 mi. NE of Arvin 4/22 8:04 am 33 53.3 116 56.7 2.2 3 mi. SSE of Beaumont 4/22 3:16 pm 35 4.9 117 32.8 2.3 23 mi. E of California City 4/22 5:50 pm 34 17.8 116 55.5 2.0 3 mi. NNW of town of Big Bear Lake 4/22 7:47 pm 32 43.5 116 1.3 2.4 1 mi. WSW of Ocotillo 4/23 2:40 am 34 5.9 116 53.8 2.0 3 mi. W of Mt. San Gorgonio 4/23 7:16 am 35 45.9 117 39.0 2.8 9 mi. N of Ridgecrest 4/23 11:26 am 33 56.6 116 21.2 2.2 8 mi. E of Desert Hot Springs 4/23 1:14 pm 35 44.0 117 41.7 2.2 7 mi. NNW of Ridgecrest 4/23 2:10 pm 34 1.2 116 23.4 2.0 7 mi. SSE of Yucca Valley 4/23 6:52 pm 35 45.8 117 38.5 2.4 9 mi. N of Ridgecrest 4/24 3:08 am 34 28.1 116 31.2 2.0 24 mi. N of Yucca Valley 4/24 5:34 am 34 24.8 116 28.3 2.1 20 mi. N of Yucca Valley 4/24 11:28 am 34 29.4 116 31.5 2.2 26 mi. N of Yucca Valley -------------------------------------------------------------