SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey October 30, 1997 Weekly Earthquake Report for Southern California ------------------------------------------------ October 23 - 29, 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 23, Universal Time (ie. UTC), to midnight Wednesday night, October 29, Universal Time. In local time, the period of coverage is from 5 p.m., October 22, Pacific Daylight Time, to 4 p.m., October 29, Pacific Standard Time. We detected 189 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 There were four M3+ quakes this week. The first was a M3.0 late in the morning on Thursday. It was an aftershock of the 1992 Landers quake (Mw7.3). There were no inquiries. The second quake of interest was on Saturday evening, a M3.1 Northridge aftershock near Simi Valley. It was apparently felt in Simi Valley. The focal mechanism was strike-slip. On Monday morning there was a M3.2 quake near Ocotillo Wells, which is in the broad San Jacinto Fault zone, west of the Salton Sea. The focal mechanism was also strike-slip. This is a sparsely populated area, and we received no inquiries. The last, and largest quake of the week, was a M3.5 near Lake Isabella on Monday evening. Again, the focal mechanism was strike-slip. This quake was felt 'in the epicentral area'. 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 ------------------------------------------------------------- PDT ... 10/22 9:34 pm 34 10.9 117 36.3 2.0 5 mi. N of Rancho Cucamonga 10/23 4:55 am 34 23.2 119 26.1 2.5 4 mi. E of Carpinteria 10/23 11:58 am 34 58.6 116 57.3 3.0 7 mi. NNE of Barstow 10/23 4:43 pm 34 8.4 120 8.7 2.3 13 mi. N of Santa Rosa Is. 10/24 10:27 am 32 51.6 118 24.3 2.2 4 mi. NW of San Clemente Is. (SE tip) 10/24 11:14 am 35 46.7 117 40.3 2.3 10 mi. N of Ridgecrest 10/25 1:05 pm 32 44.7 118 8.5 2.0 12 mi. ESE of San Clemente Is. (SE tip) 10/25 4:22 am 32 29.1 115 14.5 2.2 19 mi. SE of Calexico 10/25 12:34 pm 32 38.7 118 1.9 2.0 21 mi. ESE of San Clemente Is. (SE tip) 10/25 9:02 pm 34 15.3 118 42.4 3.1 1 mi. S of Simi Valley FELT Beginning PST ... 10/26 8:54 am 34 14.9 118 42.0 2.1 2 mi. SSE of Simi Valley 10/26 6:19 pm 33 46.7 116 9.6 2.2 5 mi. NE of Indio 10/26 7:01 pm 34 8.7 116 25.5 2.1 2 mi. NNE of Yucca Valley 10/27 5:07 am 34 25.7 116 28.6 2.1 21 mi. N of Yucca Valley 10/27 5:08 am 34 18.3 116 26.8 2.2 12 mi. N of Yucca Valley 10/27 8:41 am 33 10.6 116 2.3 3.2 5 mi. ENE of Ocotillo Wells 10/27 10:08 am 34 10.9 116 26.6 2.6 4 mi. N of Yucca Valley 10/27 3:50 pm 33 10.0 116 2.1 2.1 5 mi. ENE of Ocotillo Wells 10/27 4:55 pm 34 34.5 116 32.7 2.0 24 mi. ENE of Lucerne Valley 10/27 6:30 pm 34 8.8 116 25.4 2.0 2 mi. NE of Yucca Valley 10/27 6:32 pm 34 8.8 116 25.4 2.0 " 10/27 6:57 pm 34 8.8 116 25.3 2.0 " 10/27 8:06 pm 35 26.9 118 25.9 3.5 13 mi. S of town of Lake Isabella; FELT 10/27 11:42 pm 33 11.6 115 55.9 2.0 6 mi. SSE of Salton City 10/28 1:06 pm 34 57.1 116 46.7 2.2 14 mi. ENE of Barstow 10/28 6:04 pm 34 29.1 116 31.2 2.7 25 mi. N of Yucca Valley 10/29 9:31 am 33 13.1 116 4.9 2.1 5 mi. NNE of Ocotillo Wells 10/29 11:05 am 35 53.7 119 7.2 2.3 14 mi. SSW of Porterville -------------------------------------------------------------