SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey August 1, 1996 Weekly Earthquake Report for Southern California ------------------------------------------------ July 25 - 31, 1996 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. -------------------------------- This week's Report covers the time period from midnight Thursday morning, July 25, Universal Time (ie. GMT), to midnight Wednesday night, July 31, Universal Time. In local time, the period of coverage is from 5 p.m., July 24, Pacific Daylight Time, to 5 p.m., July 31, Pacific Daylight Time. We detected and processed 253 earthquakes during the seven-day period covered. There were two M3+ quakes this week, one of which, a M3.4 Landers aftershock in the wee hours of Sunday morning, was felt. The other was a M3.2 in San Joaquin Valley during the early hours of Saturday morning. One other quake was felt: a M2.8 Saturday evening in the Diamond Bar area. There were five quakes in the same general vicinity this week. All but the M2.8 were M2.1 or smaller and not noticed by the public. There were eleven small quakes in the Obsidian Butte area of Imperial Valley, the largest two being M2.5, one Saturday night and one yesterday afternoon. Obsidian Butte is in the northern part of the Brawley Seismic Zone, which can be a prolific source of earthquake swarms. Table 1 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 ------------------------------------------------------------- 7/24 5:48 pm 33 20.8 116 13.5 2.2 10 mi. NE of Borrego Springs 7/25 5:15 am 34 29.5 116 30.3 2.0 26 mi. N of Yucca Valley 7/25 10:12 am 33 51.8 117 44.0 2.0 4 mi. ESE of Yorba Linda 7/25 10:50 am 34 9.3 116 26.1 2.5 2 mi. NNE of Yucca Valley 7/25 5:42 pm 35 50.8 116 50.4 2.0 26 mi. SSE of Telescope Peak 7/25 9:43 pm 35 5.2 118 19.9 2.5 7 mi. ESE of Tehachapi 7/26 2:49 am 35 57.3 117 59.0 2.4 6 mi. SSW of Coso Junction 7/26 3:02 pm 33 53.2 117 51.4 2.1 2 mi. W of Yorba Linda 7/26 9:29 pm 35 57.6 117 59.2 2.5 6 mi. SSW of Coso Junction 7/26 10:22 pm 35 57.4 117 59.1 2.7 " 7/26 10:23 pm 35 57.3 117 59.5 2.0 " 7/27 2:17 am 34 9.6 116 26.4 2.0 2 mi. N of Yucca Valley 7/27 6:35 am 35 42.5 119 26.2 3.2 33 mi. NW of Bakersfield 7/27 11:06 am 36 5.3 117 43.6 2.2 12 mi. ESE of Haiwee Reservoir 7/27 2:17 pm 34 1.1 116 47.5 2.1 5 mi. SSE of Mt. San Gorgonio 7/27 11:02 pm 33 11.3 115 35.8 2.5 2 mi. ENE of Obsidian Butte 7/27 11:02 pm 33 57.2 117 49.1 2.8 3 mi. S of Diamond Bar FELT 7/27 11:04 pm 33 11.1 115 36.9 2.3 1 mi. NE of Obsidian Butte 7/28 12:08 am 34 42.6 120 13.2 2.0 6 mi. NNW of Buellton 7/28 2:46 am 33 59.5 116 16.4 3.4 10 mi. SSE of Joshua Tree FELT 7/28 4:54 am 33 59.6 116 16.4 2.3 " 7/29 3:05 am 33 46.8 116 8.3 2.1 6 mi. NE of Indio 7/29 12:18 pm 35 53.9 118 22.1 2.0 18 mi. NNE of town of Lake Isabella 7/29 10:06 pm 34 20.6 116 28.5 2.2 15 mi. N of Yucca Valley 7/29 10:12 pm 35 19.1 118 34.1 2.2 14 mi. NNW of Tehachapi 7/30 9:14 am 33 27.9 116 26.6 2.0 15 mi. NNW of Borrego Springs 7/31 4:43 pm 33 11.1 115 35.7 2.5 2 mi. ENE of Obsidian Butte -------------------------------------------------------------