SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey April 24, 1997 Weekly Earthquake Report for Southern California ------------------------------------------------ April 17 - 23, 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, April 17, Universal Time (ie. GMT), to midnight Wednesday night, April 23, Universal Time. In local time, the period of coverage is from 5 p.m., April 16, Pacific Daylight Time, to 5 p.m., April 23, Pacific Daylight Time. We detected and processed 247 earthquakes during the seven-day period covered. It was a moderately quiet week. There were three quakes of magnitude M3 and above, all of them in the Mojave Desert. The first was a M3.1 on Sunday afternoon, near the Garlock Fault, which forms the norther boundary of the Mojave. The other two were both aftershocks of the March 18, 1997 M5.1 Calico quake. These both occurred on Monday. The first and largest was a M3.6 just after midnight, and the other was a M3.0 just after noon. Neither attracted any public attention. A small quake, M2.8, was felt in Simi Valley the same day, in the early morning. It was an aftershock of the January 17, 1994 Northridge 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 ------------------------------------------------------------- 4/17 5:40 am 36 3.2 117 57.7 2.2 Under Coso Junction 4/17 9:04 pm 34 37.4 116 34.9 2.0 24 mi. ENE of Lucerne Valley 4/17 9:06 pm 32 43.3 117 24.9 2.3 10 mi. WSW of Mission Beach 4/17 10:49 pm 34 58.5 116 49.0 2.0 13 mi. ENE of Barstow 4/18 4:29 am 34 3.1 117 32.8 2.2 4 mi. SE of Rancho Cucamonga 4/18 4:03 pm 36 5.8 117 39.7 2.3 16 mi. ENE of Coso Junction 4/19 5:44 am 36 5.9 119 59.0 2.7 21 mi. E of Coalinga 4/19 5:45 am 36 5.8 119 57.2 2.5 " 4/19 3:15 pm 34 10.9 116 26.4 2.1 4 mi. N of Yucca Valley 4/19 11:52 pm 36 0.9 117 42.7 2.0 13 mi. E of Coso Junction 4/20 1:39 am 34 1.5 116 56.5 2.2 5 mi. E of Yucaipa 4/20 6:30 am 36 20.0 118 5.2 2.1 5 mi. NW of Olancha 4/20 6:53 am 34 23.3 119 31.6 2.0 Under Carpinteria 4/20 8:16 am 33 9.7 115 39.0 2.2 Under Obsidian Butte 4/20 1:31 pm 36 3.8 117 53.9 2.1 3 mi. ENE of Coso Junction 4/20 4:11 pm 35 37.0 116 54.0 3.1 18 mi. N of Goldstone Lake 4/20 6:36 pm 34 58.2 116 48.6 2.2 13 mi. ENE of Barstow 4/20 11:54 pm 34 11.4 116 48.9 2.6 5 mi. SSE of Big Bear City 4/21 12:38 am 34 58.5 116 48.7 3.6 13 mi. ENE of Barstow 4/21 2:32 am 36 2.4 119 48.4 2.3 31 mi. ESE of Coalinga 4/21 6:15 am 34 0.9 116 48.0 2.2 6 mi. SSE of Mt. San Gorgonio 4/21 8:55 am 34 17.4 118 41.7 2.8 1 mi. NE of Simi Valley FELT 4/21 12:37 pm 34 58.6 116 49.0 3.0 13 mi. ENE of Barstow 4/21 5:06 pm 35 15.2 118 35.9 2.0 12 mi. NW of Tehachapi 4/21 5:50 pm 34 7.5 116 24.3 2.0 2 mi. ENE of Yucca Valley 4/21 5:57 pm 33 50.5 117 3.7 2.4 6 mi. NE of Perris 4/21 10:54 pm 36 4.1 117 38.4 2.1 17 mi. E of Coso Junction 4/22 5:47 am 32 25.0 115 24.2 2.1 18 mi. SSE of Calexico 4/22 5:48 am 32 25.0 115 24.0 2.6 " 4/22 8:14 am 32 55.2 116 49.6 2.0 8 mi. SSE of Ramona 4/22 6:07 pm 34 58.7 116 49.0 2.2 13 mi. ENE of Barstow 4/22 10:42 pm 32 53.3 116 13.8 2.3 18 mi. SSW of Ocotillo Wells -------------------------------------------------------------