SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey February 13, 1997 Weekly Earthquake Report for Southern California ------------------------------------------------ February 6 -12, 1997 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 818-395-6327. For daily updates, call our Earthquake Information Hotline: 818-395-6977. -------------------------------- This week's Report covers the time period from midnight Thursday morning, February 6, Universal Time (ie. GMT), to midnight Wednesday night, February 12, Universal Time. In local time, the period of coverage is from 4 p.m., February 5, Pacific Standard Time, to 4 p.m., February 12, Pacific Standard Time. We detected and processed 284 earthquakes during the seven-day period covered. This week there were two events M3.5 or greater. Neither were aftershocks to any recent sequence (Coso, Ridgecrest, North- ridge, Landers) nor were reported as being felt, though they were large enough to have been. The largest was a M3.8 in Anza last Thursday evening. It was preceeded by a M1.5 foreshock 22 seconds before and since, produced 4 aftershocks above M2. Although near the San Jacinto fault, this earthquake's focal mechanism shows normal faulting on a north-striking fault. We therefore infer that it occurred on one of the many secondary faults that have formed around the very complex San Jacinto fault. The second event occurred near the California/Mexico border, near El Centro Tuesday evening. It was a M3.5. This earthquake was located near the Elsinore fault and had a focal mechanism compatible with the known right-lateral strike-slip motion of that fault. 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 ------------------------------------------------------------- 2/ 5 10:05 pm 32 25.6 115 20.2 2.5 19 mi. SSE of Calexico 2/ 5 11:32 pm 34 17.9 116 26.7 2.3 12 mi. N of Yucca Valley 2/ 6 10:45 am 36 6.5 118 13.8 2.2 17 mi. SW of Olancha 2/ 6 6:20 pm 33 6.8 118 2.9 2.5 22 mi. SE of Avalon, Catalina Island 2/ 6 7:07 pm 33 59.7 116 53.6 2.1 4 mi. N of Banning 2/ 6 10:59 pm 33 30.1 116 33.8 3.8 7 mi. ESE of Anza 2/ 6 11:09 pm 33 30.4 116 34.0 2.5 6 mi. ESE of Anza 2/ 7 1:53 am 36 16.9 118 20.4 2.0 20 mi. S of Mt. Whitney 2/ 7 6:13 am 32 26.1 115 20.4 2.5 18 mi. SSE of Calexico 2/ 7 8:52 am 36 4.0 117 38.9 2.1 16 mi. E of Coso Junction 2/ 7 11:42 am 33 16.3 116 8.7 2.1 8 mi. N of Ocotillo Wells 2/ 7 11:43 am 33 30.5 116 33.6 2.3 7 mi. ESE of Anza 2/ 7 11:44 am 33 30.5 116 33.6 2.5 " 2/ 7 6:05 pm 33 17.2 118 46.0 2.5 19 mi. NNW of San Clemente Is. (NW tip) 2/ 7 8:27 pm 33 30.2 116 33.8 2.2 7 mi. ESE of Anza 2/ 7 9:13 pm 36 5.1 117 38.0 2.3 19 mi. SSW of Panamint Springs 2/ 8 9:53 am 36 16.4 118 19.4 2.2 21 mi. S of Mt. Whitney 2/ 8 4:39 pm 34 0.6 119 0.7 2.0 4 mi. WSW of Leo Carrillo State Beach 2/ 8 10:26 pm 34 59.6 116 24.8 2.0 26 mi. SW of Baker 2/ 9 9:16 pm 35 43.3 119 36.0 2.0 34 mi. NE of Simmler 2/10 1:53 am 32 31.3 115 15.8 2.1 16 mi. SE of Calexico 2/10 2:38 am 36 5.4 117 37.5 2.0 19 mi. SSW of Panamint Springs 2/10 8:28 am 36 6.0 118 14.0 2.1 16 mi. WNW of Coso Junction 2/10 12:42 pm 36 5.4 117 39.9 2.7 16 mi. E of Coso Junction 2/10 11:32 pm 34 33.6 116 31.4 2.6 25 mi. ENE of Lucerne Valley 2/11 6:20 am 32 0.8 115 46.2 2.5 48 mi. SSW of Calexico 2/11 7:05 pm 32 37.5 115 55.1 3.5 8 mi. SSE of Ocotillo 2/12 12:41 am 32 38.1 115 54.9 2.3 " 2/12 1:38 am 36 48.8 118 34.4 2.0 22 mi. NW of Mt. Whitney 2/12 4:24 am 32 37.6 115 54.9 2.6 8 mi. SSE of Ocotillo -------------------------------------------------------------