SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey January 16, 1997 Weekly Earthquake Report for Southern California ------------------------------------------------ January 9 - 15, 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, January 9, Universal Time (ie. GMT), to midnight Wednesday night, January 15, Universal Time. In local time, the period of coverage is from 4 p.m., January 8, Pacific Standard Time, to 4 p.m., January 15, Pacific Standard Time. We detected and processed 325 earthquakes during the seven-day period covered. We had a reasonably active week this week, with four M3+ events, all but one of which was reported felt. For a change, none of them were Landers/Big Bear or Northridge aftershocks. The first was a M3.6 aftershock of the Nov. 27, 1996 Mw5.3 Coso quake, in the southern Owens Valley. The second was another M3.6 near Mt. Palomar, in northern San Diego County, near the Agua Caliente Fault, an offshoot of the Elsinore Fault, very early on Monday morning. The focal mechanism showed right-lateral strike-slip faulting on a fault striking 30 degrees west of north, consistent with the Agua Caliente. It was the one that produced no public inquiries, probably because of the sparse population in the epicentral area. The third M3+ was in the Salton City area, west of the Salton Sea, also on Monday morning. It had a magnitude of M3.5, and a strike-slip focal mechanism. It was reported felt in Salton City. This earthquake was near one of the secondary strands of the San Jacinto Fault. The fourth M3+ occurred Wedesday morning, in the Hemet area, along the San Jacinto Fault zone. It was a M3.2 and had a focal mechanism showing oblique strike-slip consistent with the strike of the San Jacinto Fault. It was felt in the Lake Perris area. Both the San Jacinto and Elsinore Faults are part of the San Andreas Fault system and are among the most active faults in California. The total number of quakes during the week was about the same as it was last week, and has been since the November '96 Coso quake. 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 ------------------------------------------------------------- 1/9 1:01 am 34 22.2 116 27.8 2.9 17 mi. N of Yucca Valley 1/9 3:06 am 36 4.5 117 38.7 2.0 17 mi. E of Coso Junction 1/9 7:01 am 36 2.3 117 42.1 2.3 13 mi. E of Coso Junction 1/9 9:03 am 36 4.5 117 38.8 2.3 17 mi. E of Coso Junction 1/9 9:11 am 34 56.7 116 47.7 2.1 13 mi. ENE of Barstow 1/9 10:56 am 36 4.8 117 38.8 2.0 17 mi. ESE of Haiwee Reservoir 1/9 11:23 am 32 26.4 115 25.9 2.9 16 mi. SSE of Calexico 1/9 6:54 pm 34 9.4 116 25.1 2.4 3 mi. NNE of Yucca Valley 1/9 7:05 pm 34 9.4 116 25.1 2.0 " 1/9 8:22 pm 34 9.1 116 25.1 2.2 2 mi. NNE of Yucca Valley 1/9 9:05 pm 34 17.3 118 20.6 2.0 1 mi. NE of Lake View Terrace 1/10 7:17 am 35 29.6 116 14.3 2.0 18 mi. NNW of Baker 1/10 8:05 am 33 44.0 120 3.5 2.9 14 mi. S of Santa Rosa Is. 1/10 1:46 pm 32 40.1 115 54.6 2.2 6 mi. SE of Ocotillo 1/10 2:37 pm 35 42.1 117 36.5 2.4 6 mi. NNE of Ridgecrest 1/11 2:52 am 34 1.4 117 14.2 2.5 1 mi. SE of Loma Linda 1/11 2:52 am 34 1.5 117 13.9 2.6 " 1/11 4:01 pm 36 3.5 117 38.3 3.6 17 mi. E of Coso Junction FELT 1/11 4:03 pm 36 3.6 117 38.2 2.4 " 1/11 4:32 pm 36 3.4 117 38.3 2.4 " 1/11 5:23 pm 36 5.6 117 39.8 2.2 15 mi. E of Haiwee Reservoir 1/12 2:15 am 36 4.2 117 39.3 2.4 16 mi. E of Coso Junction 1/12 3:33 am 34 22.5 116 27.7 2.3 17 mi. N of Yucca Valley 1/12 4:55 am 35 46.7 118 19.7 2.6 12 mi. NE of town of Lake Isabella 1/12 8:52 am 33 20.3 117 55.6 2.1 14 mi. SW of Dana Point 1/12 12:40 pm 35 18.7 118 30.2 2.1 12 mi. NNW of Tehachapi 1/12 1:49 pm 34 36.8 118 37.2 2.0 6 mi. N of Castaic Lake dam 1/12 2:15 pm 34 1.6 117 14.0 2.7 1 mi. SE of Loma Linda 1/12 2:26 pm 35 30.2 116 54.8 2.0 10 mi. N of Goldstone Lake 1/12 4:36 pm 36 3.5 117 39.5 2.3 16 mi. E of Coso Junction 1/12 7:41 pm 32 45.5 115 26.3 2.0 7 mi. NNE of Calexico 1/12 11:21 pm 35 43.2 117 39.7 2.0 6 mi. N of Ridgecrest 1/13 3:29 am 33 26.8 116 54.1 3.6 6 mi. NNW of Palomar Observatory 1/13 4:14 am 36 3.9 117 38.8 2.1 16 mi. E of Coso Junction 1/13 4:28 am 36 3.8 117 38.8 2.5 16 mi. E of Coso Junction 1/13 8:09 am 33 16.0 116 0.6 3.5 2 mi. WSW of Salton City FELT in Salton City 1/13 8:43 am 33 23.1 116 58.9 2.9 7 mi. WNW of Palomar Observatory 1/13 9:40 am 35 5.4 119 6.8 2.0 11 mi. WNW of Wheeler Ridge 1/13 4:46 pm 34 13.0 117 32.8 2.2 8 mi. NNE of Rancho Cucamonga 1/14 6:04 am 36 5.7 117 40.2 2.2 15 mi. E of Haiwee Reservoir 1/14 11:15 am 34 23.6 118 49.6 2.2 5 mi. E of Fillmore 1/14 7:23 pm 34 49.0 118 56.3 2.2 Under Frazier Park 1/14 9:01 pm 34 24.1 119 43.1 2.2 1 mi. SW of downtown Santa Barbara 1/15 7:02 am 33 49.2 117 0.1 2.1 5 mi. NNW of Hemet 1/15 8:17 am 33 49.2 117 0.1 3.2 " FELT in Perris Lake area 1/15 1:25 pm 33 49.3 117 0.1 2.0 " -------------------------------------------------------------