SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey January 22, 1998 Weekly Earthquake Report for Southern California ------------------------------------------------ January 15 - 21, 1998 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. -------------------------------- ****************************************************************** As many of you know by now, the U.S. Geological Survey in Menlo Park, the office which originates the Northern California Earthquake Report, is planning to discontinue the paper (and faxed) Report at the end of January 1998. We plan to follow their initiative. As of the beginning of February 1998, we will be replacing our weekly 'treeware' product with a Web site, which will include the same map, table, and commentary as the current Weekly Report, plus other features. The Web page will be updated more often than once per week. You will be able to get to this web site form the following home pages: http://www.gps.caltech.edu/seismo/ http://www-socal.wr.usgs.gov/ http://www.scecdc.scec.org/ http://www.trinet.org/ (The last one does not exist yet, but will soon.) There will be no paper copy or usenet distribution. We hope we are giving our Users sufficient notice to obtain World Wide Web access for themselves. At minimum, most public libraries now provide Web access, along with the capability to print copies of Web pages. ****************************************************************** This week's Report covers the time period from midnight Wednesday morning, January 15, Universal Time (ie. UTC), to midnight Wednesday night, January 21, Universal Time. In local time, the period of coverage is from 4 p.m., January 14, Pacific Standard Time, to 4 p.m., January 21, Pacific Standard Time. We detected 199 earthquakes during the seven-day period covered. We had a quiet week this week. The largest event inside the coverage area, and the only one felt, was a M2.9 Northridge aftershock in the Pacoima area on Thursday afternoon. It occurred on the very eastern edge of the aftershock zone, with an oblique thrusting focal mechanism. 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 ------------------------------------------------------------- 1/15 1:00 am 34 17.4 116 56.2 2.1 3 mi. NNW of town of Big Bear Lake 1/15 6:24 am 34 44.0 120 21.4 2.1 8 mi. NE of Lompoc 1/15 2:54 pm 34 15.9 118 26.0 2.9 1 mi. SSE of Pacoima FELT 1/15 4:57 pm 33 9.4 116 27.4 2.3 8 mi. SW of Borrego Springs 1/15 11:25 pm 34 20.4 116 27.7 2.2 15 mi. N of Yucca Valley 1/15 11:48 pm 34 8.7 116 44.2 2.7 6 mi. ENE of Mt. San Gorgonio 1/16 6:57 am 33 11.6 115 36.5 2.0 2 mi. NE of Obsidian Butte 1/16 5:01 pm 34 15.6 117 11.1 2.2 Under Lake Arrowhead 1/17 1:39 pm 33 41.8 117 28.4 2.0 8 mi. WNW of Lake Elsinore 1/17 11:08 pm 32 12.2 115 35.0 3.1 32 mi. S of Calexico 1/18 9:49 am 36 17.5 118 4.2 2.3 3 mi. W of Olancha 1/18 1:37 pm 36 9.9 118 0.7 2.6 8 mi. S of Olancha 1/19 1:10 am 32 55.1 116 14.9 2.3 16 mi. SSW of Ocotillo Wells 1/19 4:45 am 32 45.5 118 6.9 2.6 14 mi. ESE of San Clemente Is. (SE tip) 1/19 8:21 am 36 5.8 118 13.7 2.0 16 mi. WNW of Coso Junction 1/19 10:40 am 34 0.9 117 13.8 2.3 2 mi. SSE of Loma Linda 1/19 12:20 pm 33 44.3 117 29.9 2.0 10 mi. SSE of Corona 1/20 2:18 am 36 12.4 120 11.6 2.8 10 mi. ENE of Coalinga 1/20 2:11 pm 32 10.7 115 36.6 3.2 34 mi. S of Calexico 1/21 3:34 am 34 20.9 118 44.9 2.1 5 mi. NNW of Simi Valley 1/21 9:05 am 34 27.9 118 36.0 2.0 4 mi. SSE of Castaic Lake dam -------------------------------------------------------------