SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey July 25, 1996 Weekly Earthquake Report for Southern California ------------------------------------------------ July 18 - 24, 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 18, Universal Time (ie. GMT), to midnight Wednesday night, July 24, Universal Time. In local time, the period of coverage is from 5 p.m., July 17, Pacific Daylight Time, to 5 p.m., July 24, Pacific Daylight Time. We detected and processed 252 earthquakes during the seven-day period covered. There were three M3+ earthquakes this week, but, as far as we know, only one was felt. That one was a M3.4 early Sunday morning in the San Gorgonio Pass area. It was not an aftershock of any larger event. It was located between the two strands of the San Andreas fault, a common site for M3+ events. Its focal mechanism shows right-lateral strike-slip motion on an east- striking vertical fault. The two other M3+ shocks were: a M3.0 in the Death Valley area, also on Sunday morning, and a M3.2 near Barstow on Tuesday morning. The Barstow quake was an aftershock of the June 28, 1992 Mw7.3 Landers earthquake, but the Death Valley event was not an aftershock. The Death Valley had several smaller earth- quakes as well this week, somewhat more than its average rate. Of interest among the smaller earthquakes were several events smaller than M2 in the Santa Barbara Channel. The Channel is a sporadic producer of earthquakes, alternating between periods of complete quiet, times with many small events and occasional larger 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 ------------------------------------------------------------- 7/18 8:25 am 34 20.6 116 28.1 2.1 15 mi. N of Yucca Valley 7/18 1:18 pm 34 18.9 116 27.0 2.1 13 mi. N of Yucca Valley 7/18 2:41 pm 35 45.4 117 39.1 2.1 9 mi. N of Ridgecrest 7/18 10:18 pm 33 40.6 116 21.2 2.0 3 mi. SE of Palm Desert 7/18 11:52 pm 34 28.2 116 30.3 2.1 24 mi. N of Yucca Valley 7/19 12:27 pm 34 38.2 116 40.5 2.3 20 mi. NE of Lucerne Valley 7/19 12:32 pm 35 48.1 117 37.2 2.3 12 mi. NNE of Ridgecrest 7/19 5:43 pm 34 45.6 120 52.8 2.2 15 mi. SW of Pt. Sal 7/19 9:17 pm 33 54.7 118 18.5 2.1 2 mi. E of Hawthorne 7/20 2:28 am 36 9.0 118 26.8 2.0 30 mi. SSW of Mt. Whitney 7/20 2:48 am 36 6.3 118 24.7 2.2 25 mi. WSW of Olancha 7/21 2:21 am 34 15.3 118 28.6 2.3 1 mi. SE of Granada Hills 7/21 3:16 am 33 16.8 116 13.4 2.1 8 mi. E of Borrego Springs 7/21 5:53 am 33 59.8 116 48.8 3.4 5 mi. NNW of Cabazon FELT 7/21 5:53 am 33 59.9 116 48.8 2.0 5 mi. NNW of Cabazon 7/21 8:38 am 35 49.2 116 35.2 3.0 20 mi. WSW of Shoshone 7/22 8:23 pm 33 32.4 116 26.3 2.0 12 mi. SSW of Palm Desert 7/23 2:46 am 36 4.9 117 52.7 2.0 4 mi. ENE of Coso Junction 7/23 5:06 am 36 26.8 120 3.9 2.5 25 mi. SW of Fresno 7/23 7:01 am 34 60.0 116 56.9 2.3 8 mi. NNE of Barstow 7/23 7:02 am 35 0.0 116 56.9 3.2 " 7/23 8:29 am 34 24.6 116 27.0 2.3 20 mi. N of Yucca Valley 7/24 12:08 am 35 23.6 117 13.6 2.0 19 mi. W of Goldstone Lake 7/24 12:27 am 33 54.8 116 20.4 2.8 9 mi. ESE of Desert Hot Springs 7/24 1:03 am 36 0.8 117 48.8 2.9 Coso Range, 7 mi. ESE of Coso Junction 7/24 3:24 am 35 41.0 117 36.1 2.8 5 mi. NE of Ridgecrest 7/24 4:32 am 35 51.0 116 51.2 2.2 25 mi. SSE of Telescope Peak 7/24 10:36 am 35 50.7 116 51.5 2.2 " 7/24 12:20 pm 35 51.2 116 50.8 2.5 " -------------------------------------------------------------