SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey October 16, 1997 Weekly Earthquake Report for Southern California ------------------------------------------------ October 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 626-395-6327. For daily updates, call our Earthquake Information Hotline: 626-395-6977. -------------------------------- ***************************************************************** If you receive this Report by FAX and if you have recently had a change of AREA CODE, please notify us ASAP. We have no other way to know which fax numbers need to be changed!! Actually, if your area code is 818 and it HASN'T changed, it would be helpful to know that, too. ***************************************************************** This week's Report covers the time period from midnight Thursday morning, October 9, Universal Time (ie. UTC), to midnight Wednesday night, October 15, Universal Time. In local time, the period of coverage is from 5 p.m., October 8, Pacific Daylight Time, to 5 p.m., October 15, Pacific Daylight Time. We detected 196 earthquakes during the seven-day period covered. These Weekly Reports should not be used for archival purposes. Further data processing often changes the magnitudes slightly and, especially during times of high seismicity, sometimes changes the estimates of total seismicity. For the best earthquake catalog currently available, see: http://scec.gps.caltech.edu/catalog-search.html The week's largest event, and the only one for which we had public inquiries, was a M3.9 under Fontana on Tuesday afternoon. It had a mostly strike-slip focal mechanism, consistent with the usual northwest-southeast (or northeast- southwest) trends that we see in the region. Note that the location of this quake tells us that it is not on either the San Jacinto Fault or the Cucamonga Fault. This quake was widely felt in the Inland Empire. There was one other M3+ event. It was a Landers after- shock on Tuesday evening, in the Barstow area. Typical of Landers aftershocks, it was also a strike-slip 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 ------------------------------------------------------------- 10/8 6:08 pm 36 0.3 117 23.7 2.0 16 mi. N of Trona 10/8 8:47 pm 32 56.7 116 1.9 2.1 14 mi. N of Ocotillo 10/8 9:11 pm 35 6.8 119 2.4 2.7 9 mi. NW of Wheeler Ridge 10/8 11:32 pm 32 51.5 115 59.3 2.2 8 mi. N of Ocotillo 10/9 12:13 am 32 36.2 115 41.2 2.3 12 mi. WSW of Calexico 10/9 4:47 am 34 21.5 116 40.5 2.2 12 mi. ENE of Big Bear City 10/9 6:51 am 34 22.8 116 28.1 2.2 18 mi. N of Yucca Valley 10/10 11:17 am 33 56.1 116 1.5 2.1 14 mi. S of Twentynine Palms 10/10 11:17 am 33 56.3 116 1.4 2.0 " 10/10 11:17 am 33 56.3 116 1.2 2.3 " 10/10 3:02 pm 34 14.1 119 42.3 2.2 12 mi. S of downtown Santa Barbara 10/10 4:55 pm 33 9.4 116 0.9 2.3 6 mi. E of Ocotillo Wells 10/10 8:58 pm 33 59.4 116 50.0 2.6 5 mi. NNE of Banning 10/11 4:04 am 34 10.7 116 26.6 2.1 4 mi. N of Yucca Valley 10/11 11:39 am 32 12.8 115 48.9 2.6 37 mi. SSE of Ocotillo 10/11 12:03 pm 33 45.3 116 7.7 2.8 5 mi. ENE of Indio 10/11 7:43 pm 33 37.5 118 35.7 2.6 14 mi. SW of Palos Verdes Point 10/12 1:56 am 33 56.2 116 1.2 2.3 13 mi. S of Twentynine Palms 10/12 6:44 pm 34 21.3 116 53.3 2.2 6 mi. NNW of Big Bear City 10/12 8:40 pm 34 26.8 119 12.2 2.6 2 mi. E of Ojai 10/12 10:11 pm 32 35.9 115 41.5 2.0 12 mi. WSW of Calexico 10/12 11:11 pm 34 10.6 116 26.4 2.0 4 mi. N of Yucca Valley 10/13 12:50 am 34 10.8 116 26.1 2.0 " 10/13 1:00 am 34 10.8 116 26.4 2.1 " 10/13 2:41 am 33 10.7 116 2.6 2.2 5 mi. ENE of Ocotillo Wells 10/13 11:47 am 35 47.2 117 37.5 2.0 11 mi. NNE of Ridgecrest 10/14 3:33 am 33 58.3 116 57.2 2.0 3 mi. NNE of Beaumont 10/14 4:00 am 36 12.6 117 33.1 2.3 24 mi. ENE of Coso Junction 10/14 4:56 am 32 33.0 117 59.7 2.5 27 mi. SE of San Clemente Is. (SE tip) 10/14 7:13 am 35 22.2 118 50.3 2.2 9 mi. E of Bakersfield 10/14 3:31 pm 34 6.6 117 25.9 3.9 Under Fontana WIDELY FELT 10/14 4:33 pm 34 6.2 117 26.6 2.0 " 10/14 8:21 pm 34 57.8 116 50.3 3.2 11 mi. ENE of Barstow 10/15 2:23 am 34 8.4 116 26.5 2.2 1 mi. N of Yucca Valley 10/15 1:57 pm 34 15.1 117 40.7 2.3 2 mi. SW of Mt. Baldy -------------------------------------------------------------