SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey May 15, 1997 Weekly Earthquake Report for Southern California ------------------------------------------------ May 8 - 14, 1997 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 818-395-6327. For daily updates, call our Earthquake Information Hotline: 818-395-6977. -------------------------------- This week's Report covers the time period from midnight Thursday morning, May 8, Universal Time (ie. GMT), to midnight Wednesday night, May 14, Universal Time. In local time, the period of coverage is from 5 p.m., May 7, Pacific Daylight Time, to 5 p.m., May 14, Pacific Daylight Time. We detected 238 earthquakes during the seven-day period covered. This week's largest quake was a M3.8 that occurred late Saturday afternoon, in the San Gorgonio Pass area, southwest of Morongo Valley and northwest of Palm Springs. It was fairly widely felt in the Palm Springs and Desert Hot Springs areas. The focal mechanism was obligue thrust, on a plane striking northwest, with a dip to the northeast, with mostly right-lateral strike-slip and a small component of thrust. Historically, this event is just to the west, and in the foot wall, of the July 8, 1986 ML5.6 North Palm Springs zone. This week's quake had one M2.5 aftershock. The only other M3+ quake was a M3.0 Ridgecrest event just before midnight last Wednesday night. There was also a M2.5 that generated a couple of public inquiries. It was in the wee hours last Thursday morning, and was an aftershock of the April 27 and 27 (M5.1 and M4.9) Northridge aftershocks. 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 ------------------------------------------------------------- 5/7 5:28 pm 35 39.7 118 32.2 2.2 4 mi. WNW of town of Lake Isabella 5/7 6:58 pm 34 59.0 116 56.2 2.0 8 mi. NE of Barstow 5/7 11:59 pm 35 43.7 117 37.5 3.0 7 mi. NNE of Ridgecrest 5/7 11:59 pm 35 43.3 117 37.0 2.2 " 5/8 1:26 am 34 22.9 118 38.9 2.5 4 mi. W of Valencia POSSIBLY FELT 5/8 7:35 pm 33 24.6 115 44.6 2.1 4 mi. N of Bombay Beach 5/9 11:10 am 34 49.4 120 18.1 2.7 11 mi. SE of Santa Maria 5/9 11:38 am 34 1.6 118 11.5 2.2 1 mi. WSW of East Los Angeles 5/9 2:43 pm 33 1.3 116 20.8 2.0 16 mi. S of Borrego Springs 5/9 6:21 pm 34 23.0 118 38.5 2.2 4 mi. W of Valencia 5/9 7:22 pm 34 49.0 120 18.9 2.4 11 mi. SE of Santa Maria 5/9 9:50 pm 34 60.0 116 57.5 2.4 8 mi. NNE of Barstow 5/10 1:06 am 34 22.6 116 27.6 2.4 17 mi. N of Yucca Valley 5/10 4:40 am 36 27.0 117 54.5 2.6 12 mi. NNE of Olancha 5/10 5:16 pm 33 58.4 116 40.3 3.8 7 mi. SW of Morongo Valley; FELT 5/10 5:24 pm 33 58.6 116 40.5 2.5 " 5/10 5:27 pm 35 57.6 117 39.4 2.2 17 mi. ESE of Coso Junction 5/11 8:40 am 34 2.1 116 55.0 2.1 6 mi. SW of Mt. San Gorgonio 5/11 6:34 pm 33 16.2 116 5.6 2.3 7 mi. W of Salton City 5/12 4:19 am 34 49.3 120 18.8 2.2 11 mi. SE of Santa Maria 5/12 5:18 am 34 20.9 116 28.2 2.1 15 mi. N of Yucca Valley 5/12 8:14 pm 36 3.9 117 38.2 2.1 17 mi. E of Coso Junction 5/12 8:50 pm 34 20.4 116 28.4 2.2 15 mi. N of Yucca Valley 5/12 11:46 pm 35 22.3 117 15.1 2.4 20 mi. W of Goldstone Lake 5/13 4:29 am 34 56.9 116 49.7 2.3 11 mi. ENE of Barstow 5/13 5:27 am 32 51.2 116 14.4 2.0 16 mi. WNW of Ocotillo 5/13 10:59 am 32 3.3 116 17.6 2.6 50 mi. SSW of Ocotillo 5/13 1:04 pm 36 17.4 120 23.4 2.8 10 mi. N of Coalinga 5/13 3:56 pm 32 30.7 118 11.4 2.7 23 mi. SSE of San Clemente Is. (SE tip) 5/13 4:42 pm 34 23.0 118 38.7 2.0 4 mi. W of Valencia -------------------------------------------------------------