SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey May 22, 1997 Weekly Earthquake Report for Southern California ------------------------------------------------ May 15 - 21, 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 15, Universal Time (ie. GMT), to midnight Wednesday night, May 21, Universal Time. In local time, the period of coverage is from 5 p.m., May 14, Pacific Daylight Time, to 5 p.m., May 21, Pacific Daylight Time. We detected 226 earthquakes during the seven-day period covered. Although the weekly total was about the same as it has been for the past few weeks, there were five M3+ quakes this week, all but one of which was reported felt. Two of them were aftershocks to the Landers/Big Bear earthquakes (June 28, 1992 Mw7.3 and Mw6.2). A M3.1 aftershock occurred last Thursday morning, just north of the epicenter of the Big Bear quake, and was felt at Big Bear Lake. Like most of the Landers sequence, this earthquake had a strike-slip focal mechanism. The other notable Landers aftershock this week occurred at the other end of the aftershock zone: a M3.0 on Friday afternoon near Barstow. The latter managed to escape public notice. On Thursday morning, a M3.1 occurred offshore of Manhattan Beach, and was felt in the South Bay area. This event had an oblique thrust mechanism, common in the fold and thrust belt that lies offshore. On Sunday afternoon, another M3.1 earthquake occurred near Santa Maria and was also felt locally. Very early Friday morning, a M3.2 in northern Mexico was felt in the greater San Diego area. One more, smaller, quake was felt: a M2.7 in the Anza area on Friday night was felt in Palm Springs. 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 ------------------------------------------------------------- 5/15 4:07 am 34 26.4 116 30.8 2.4 22 mi. N of Yucca Valley 5/15 4:32 am 33 28.3 118 15.7 2.1 9 mi. NNE of Avalon, Catalina Island 5/15 5:57 am 32 47.4 115 27.3 2.3 5 mi. E of El Centro 5/15 6:11 am 32 47.8 115 27.3 2.1 " 5/15 6:26 am 32 47.2 115 27.5 2.4 " 5/15 6:31 am 34 22.3 116 52.7 3.1 6 mi. SE of Lucerne Valley FELT in Big Bear Lake 5/15 7:29 am 33 52.7 118 27.6 3.1 3 mi. W of Manhattan Beach FELT 5/15 2:28 pm 33 55.8 116 17.1 2.1 14 mi. S of Joshua Tree 5/15 7:41 pm 36 5.7 117 39.7 2.2 16 mi. ENE of Coso Junction 5/15 7:42 pm 36 6.2 117 39.7 2.8 " 5/16 12:15 am 34 0.8 118 57.8 2.1 2 mi. SW of Leo Carrillo State Beach 5/16 1:19 am 34 38.8 119 31.7 2.8 17 mi. N of Carpinteria 5/16 1:54 am 34 1.7 118 57.7 2.1 1 mi. SW of Leo Carrillo State Beach 5/16 3:34 am 32 13.7 116 41.5 3.2 30 mi. SE of San Ysidro FELT in La Mesa 5/16 5:45 am 33 28.4 118 15.5 2.6 9 mi. NNE of Avalon, Catalina Island 5/16 12:36 pm 33 21.3 116 21.6 2.9 6 mi. N of Borrego Springs 5/16 12:43 pm 35 46.9 117 39.4 2.6 11 mi. N of Ridgecrest 5/16 3:20 pm 34 58.1 116 56.4 3.0 7 mi. NE of Barstow 5/16 9:02 pm 34 21.2 116 27.4 2.3 16 mi. N of Yucca Valley 5/16 10:29 pm 33 37.8 116 45.3 2.7 7 mi. NW of Anza FELT in Palm Springs 5/16 10:56 pm 33 37.7 116 45.1 2.7 " 5/17 12:52 am 32 31.0 118 12.1 2.2 22 mi. SSE of San Clemente Is. (SE tip) 5/17 9:46 pm 32 36.3 115 53.5 2.0 10 mi. SSE of Ocotillo 5/18 12:17 am 36 7.0 118 2.8 2.0 7 mi. NW of Coso Junction 5/18 12:42 am 33 56.9 117 4.4 2.1 6 mi. SSW of Yucaipa 5/18 7:27 am 34 37.4 116 32.3 2.0 26 mi. ENE of Lucerne Valley 5/18 1:13 pm 33 47.7 116 58.9 2.2 3 mi. N of Hemet 5/18 2:45 pm 34 48.8 120 18.5 3.1 11 mi. SE of Santa Maria FELT 5/18 7:52 pm 36 5.8 117 39.8 2.1 16 mi. ENE of Coso Junction 5/18 9:06 pm 35 58.8 118 18.6 2.0 20 mi. WSW of Coso Junction 5/18 10:41 pm 33 39.3 116 46.7 2.3 7 mi. SSW of Idyllwild 5/18 10:41 pm 34 22.2 116 52.5 2.2 6 mi. SE of Lucerne Valley 5/19 1:18 am 34 58.3 116 48.9 2.0 13 mi. ENE of Barstow 5/19 6:15 am 34 22.4 116 52.8 2.2 6 mi. SE of Lucerne Valley 5/19 6:17 am 35 13.3 117 14.3 2.8 21 mi. WSW of Goldstone Lake 5/19 8:01 am 34 57.0 116 49.4 2.5 12 mi. ENE of Barstow 5/19 10:07 am 35 51.4 117 21.1 2.1 6 mi. N of Trona 5/19 11:09 am 34 58.3 116 48.7 2.1 13 mi. ENE of Barstow 5/19 3:54 pm 34 55.2 116 54.9 2.8 6 mi. ENE of Barstow 5/20 12:35 pm 35 49.3 117 52.8 2.0 15 mi. SSE of Coso Junction 5/20 4:18 pm 33 55.4 116 19.9 2.5 10 mi. ESE of Desert Hot Springs -------------------------------------------------------------