SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey February 5, 1998 Weekly Earthquake Report for Southern California ------------------------------------------------ January 29 - February 4, 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 February 1998. We plan to follow their initiative. As of the beginning of March 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 29, Universal Time (ie. UTC), to midnight Wednesday night, February 4, Universal Time. In local time, the period of coverage is from 4 p.m., January 28, Pacific Standard Time, to 4 p.m., February 4, Pacific Standard Time. We detected 152 earthquakes during the seven-day period covered. Note that we have decided to extend the production of the Weekly Report through February, or until we have thoroughly tested some of our newest software. This week was a quiet week. There were only two earthquakes worth mentioning. The first was a M3.0 Northridge aftershock during the wee hours on Saturday. It was felt in the northern part of the San Fernando Valley. Like most of the Northridge after- shocks, it had a thrust focal mechanism. The other one was a M3.5 in the San Bernardino Mtns. on Tuesday morning. The epicenter was near Mill Creek Canyon, to the east-northeast of Yucaipa. It was felt. It had a focal mechanism showing oblique strike-slip and thrust faulting, consistent with the local stress regime. 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 ------------------------------------------------------------- 1/28 4:46 pm 32 13.3 115 47.2 2.5 35 mi. SSW of Calexico 1/29 6:13 am 33 23.9 116 36.7 2.0 11 mi. SSE of Anza 1/29 12:19 pm 35 20.5 118 31.5 2.9 15 mi. NNW of Tehachapi 1/29 4:41 pm 32 6.0 118 46.5 2.7 55 mi. SSW of San Clemente Is. (SE tip) 1/30 3:25 am 34 18.3 118 28.5 3.0 2 mi. NNE of Granada Hills FELT 1/30 11:09 am 34 20.4 116 28.1 2.1 15 mi. N of Yucca Valley 1/30 7:40 pm 35 4.0 116 59.8 2.1 12 mi. N of Barstow 1/31 9:28 am 36 25.4 117 52.1 2.2 12 mi. NE of Olancha 1/31 10:31 am 32 13.9 115 9.2 2.6 36 mi. SSE of Calexico 1/31 8:01 pm 32 30.5 115 31.0 2.5 11 mi. S of Calexico 1/31 11:29 pm 34 18.6 116 51.0 2.3 3 mi. N of Big Bear City 2/1 6:55 pm 32 44.1 115 29.8 2.0 4 mi. N of Calexico 2/1 9:06 pm 35 14.6 118 35.8 2.1 11 mi. NW of Tehachapi 2/2 4:47 am 34 58.1 116 48.9 2.0 13 mi. ENE of Barstow 2/2 10:21 am 36 57.9 117 55.6 2.6 18 mi. NE of Independence 2/3 5:43 am 33 32.4 116 33.6 2.1 6 mi. E of Anza 2/3 8:45 am 34 6.7 116 54.9 3.5 5 mi. W of Mt. San Gorgonio FELT 2/3 1:06 pm 32 31.9 115 17.7 2.0 14 mi. SE of Calexico 2/3 2:54 pm 35 7.0 117 18.7 2.0 20 mi. ENE of Boron 2/3 9:54 pm 32 58.6 115 46.2 2.0 9 mi. WSW of Westmorland 2/4 2:38 am 32 27.1 115 14.2 2.6 21 mi. SE of Calexico 2/4 2:13 pm 32 6.6 115 38.3 2.4 39 mi. SSW of Calexico -------------------------------------------------------------