SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey May 23, 1996 Weekly Earthquake Report for Southern California ------------------------------------------------ May 16 - 22, 1996 Prepared by: 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, May 16, Universal Time (ie. GMT), to midnight Wednesday night, May 22, Universal Time. In local time, the period of coverage is from 5 p.m., May 15, Pacific Daylight Time, to 5 p.m., May 22, Pacific Daylight Time. We detected and processed 276 earthquakes during the 7-day period covered. The largest earthquake this week, a M3.5 was also the largest earthquake in a swarm that started Tuesday evening near the southern end of the Salton Sea. The swarm produced three earthquakes M3 or greater (all of which were felt) and over 25 other events between M2.0 - M2.9. This location, near Obsidian Buttes, has been the source of many such swarms over the last 7 years. It is at the northern end of a trend of seismicity called the Brawley Seismic Zone. This zone is thought to be part of the system that transmits plate tectonic motion from the Gulf of California to the San Andreas fault. Like most Brawley Seismic Zone earthquakes, this week's events occurred on a strike-slip fault. On Monday morning the people in the Indio area felt a M3.3 and on Tuesday morning I received a call from a woman who convinced me she felt the M2.1 at 3:10 a.m. just of east of the Los Angeles International Airport. 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 ------------------------------------------------------------- 5/16 6:13 am 34 7.1 116 58.5 2.2 6 mi. NNE of Yucaipa 5/16 12:56 pm 36 6.9 120 0.6 2.7 19 mi. E of Coalinga 5/16 12:58 pm 33 58.0 117 0.8 2.2 3 mi. NW of Beaumont 5/16 6:14 pm 32 53.0 117 40.4 2.1 24 mi. W of La Jolla 5/17 11:59 am 35 56.5 117 36.8 2.9 18 mi. NW of Trona 5/17 12:09 pm 33 52.6 118 18.6 2.1 3 mi. SE of Hawthorne 5/17 1:18 pm 33 11.0 115 36.0 2.5 2 mi. ENE of Obsidian Butte 5/17 1:20 pm 33 10.9 115 35.8 2.0 " 5/17 2:17 pm 33 10.6 115 35.6 2.1 " 5/17 5:22 pm 35 44.5 117 40.2 2.4 8 mi. N of Ridgecrest 5/18 7:22 am 36 5.5 117 52.5 2.0 5 mi. SE of Haiwee Reservoir 5/18 8:41 am 32 15.7 116 26.8 2.0 42 mi. SW of Ocotillo 5/18 10:39 am 33 13.9 116 12.2 2.0 7 mi. NW of Ocotillo Wells 5/19 12:43 am 34 22.1 118 39.9 2.5 6 mi. NNE of Simi Valley 5/19 10:48 am 36 24.0 117 56.6 2.0 8 mi. NNE of Olancha 5/19 8:18 pm 35 25.5 118 53.7 2.3 6 mi. ENE of Bakersfield 5/19 8:45 pm 35 23.4 117 14.4 2.1 20 mi. W of Goldstone Lake 5/19 11:42 pm 35 44.5 117 40.4 2.1 8 mi. N of Ridgecrest 5/20 2:04 am 32 47.7 115 27.4 2.5 5 mi. E of El Centro 5/20 2:19 am 32 48.7 115 27.9 2.0 " 5/20 2:37 am 32 47.7 115 27.5 2.3 " 5/20 5:08 am 32 28.1 116 54.4 2.1 9 mi. SE of San Ysidro 5/20 10:12 am 33 20.8 116 13.3 3.3 10 mi. NE of Borrego Springs FELT 5/21 3:10 am 33 57.5 118 24.3 2.1 1 mi. ENE of Los Angeles Airport; FELT 5/21 5:43 pm 34 11.9 118 34.3 2.3 1 mi. E of Canoga Park 5/21 6:16 pm 33 11.1 115 35.9 2.1 2 mi. ENE of Obsidian Butte 5/21 6:42 pm 33 10.6 115 36.4 2.5 1 mi. ENE of Obsidian Butte 5/21 8:12 pm 33 57.5 118 33.2 2.0 5 mi. SW of Santa Monica 5/21 8:46 pm 33 9.0 115 38.6 2.3 1 mi. SSW of Obsidian Butte 5/21 8:47 pm 33 9.0 115 38.7 2.6 " 5/21 8:47 pm 33 8.8 115 38.4 2.0 " 5/21 8:48 pm 33 9.2 115 38.7 2.5 " 5/21 8:49 pm 33 9.3 115 39.1 2.7 " 5/21 8:49 pm 33 9.1 115 38.5 3.0 1 mi. SSW of Obsidian Butte FELT 5/21 8:50 pm 33 8.9 115 39.0 2.0 " 5/21 8:51 pm 33 9.0 115 38.5 2.3 " 5/21 8:53 pm 33 9.1 115 38.8 2.2 " 5/21 9:22 pm 33 8.9 115 38.0 2.3 " 5/21 9:22 pm 33 9.0 115 38.7 3.3 1 mi. SSW of Obsidian Butte FELT 5/21 9:23 pm 33 7.0 115 38.1 2.7 3 mi. S of Obsidian Butte 5/21 9:24 pm 33 9.1 115 38.2 2.5 " 5/21 9:26 pm 33 8.9 115 38.2 2.8 " 5/21 9:32 pm 33 9.2 115 38.5 2.7 " 5/21 9:32 pm 33 8.0 115 39.5 2.0 2 mi. SSW of Obsidian Butte 5/21 9:33 pm 33 9.6 115 38.1 2.0 Under Obsidian Butte 5/21 9:43 pm 33 8.6 115 38.8 2.4 1 mi. SSW of Obsidian Butte 5/21 9:49 pm 33 8.6 115 39.2 2.6 2 mi. SSW of Obsidian Butte 5/21 9:54 pm 33 8.5 115 38.3 2.3 " 5/21 10:02 pm 33 8.5 115 38.4 2.3 1 mi. S of Obsidian Butte 5/21 10:08 pm 33 9.0 115 38.5 2.2 " 5/21 10:10 pm 33 8.7 115 38.8 2.3 " 5/21 10:30 pm 33 8.7 115 38.4 2.1 " 5/21 10:54 pm 33 8.7 115 38.7 3.5 1 mi. S of Obsidian Butte FELT 5/22 1:56 am 33 11.0 115 35.8 2.3 2 mi. ENE of Obsidian Butte 5/22 7:47 am 33 8.7 115 38.2 2.1 1 mi. S of Obsidian Butte 5/22 12:41 pm 34 20.5 116 28.2 2.4 15 mi. N of Yucca Valley 5/22 1:14 pm 34 36.9 116 39.7 2.1 19 mi. NE of Lucerne Valley 5/22 4:45 pm 34 28.8 116 30.9 2.4 25 mi. N of Yucca Valley -------------------------------------------------------------