SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey June 5, 1997 Weekly Earthquake Report for Southern California ------------------------------------------------ May 29 - June 4, 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 29, Universal Time (ie. GMT), to midnight Wednesday night, June 4, Universal Time. In local time, the period of coverage is from 5 p.m., May 28, Pacific Daylight Time, to 5 p.m., June 4, Pacific Daylight Time. We detected 241 earthquakes during the eight-day period covered. The 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 available, see: http://scec.gps.caltech.edu/catalog-search.html There was only one M3+ quake this week, and it was the only one felt. It occurred near Mt. Palomar, in San Diego County, late last Thursday afternoon and had a magnitude of M3.4. This quake was felt slightly in the Escondido area. It was located close to the Elsinore Fault, which is one of the major strike-slip faults of the San Andreas system, but it had an oblique thrust focal mechanism and therefore probably occurred on a secondary fault. Those who stare at the accompanying map might notice a small cluster of earthquakes near the San Andreas Fault northeast of Santa Maria in the Carrizo Plain. Six quakes occurred there this week, the largest of which was M2.5. Although there were very small and thus not of great significance, these events are moderately unusual. A M3.0 occurred very close to this location in 1978. This week's events are probably not on the San Andreas Fault itself. Our location capability is good in that area, and these hypocenters are more than 2 km off of the San Andreas. 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 ------------------------------------------------------------- 5/28 5:48 pm 33 20.8 116 54.7 3.4 2 mi. W of Palomar Observatory; FELT in Escondido 5/29 6:02 am 34 37.8 116 34.0 2.5 25 mi. ENE of Lucerne Valley 5/29 7:05 am 36 3.6 117 52.2 2.1 4 mi. ENE of Coso Junction 5/29 9:37 am 34 55.4 116 54.8 2.1 6 mi. ENE of Barstow 5/30 12:21 am 34 54.6 120 51.8 2.5 10 mi. W of Pt. Sal 5/30 12:54 pm 35 16.9 119 53.8 2.0 7 mi. SE of Simmler 5/30 4:15 pm 33 33.9 117 2.5 2.6 13 mi. SSW of Hemet 5/30 11:29 pm 35 59.0 117 40.2 2.0 16 mi. ESE of Coso Junction 5/31 3:39 am 34 22.2 118 39.4 2.1 5 mi. WSW of Valencia 5/31 1:22 pm 36 4.8 117 38.1 2.0 17 mi. E of Coso Junction 5/31 11:34 pm 34 16.7 116 26.9 2.3 11 mi. N of Yucca Valley 6/1 3:38 am 35 17.1 119 53.3 2.0 7 mi. SE of Simmler 6/2 12:10 am 34 37.8 116 30.1 2.0 28 mi. ENE of Lucerne Valley 6/2 1:25 am 34 9.0 116 24.7 2.1 2 mi. NE of Yucca Valley 6/2 4:16 am 34 16.7 118 32.9 2.1 3 mi. NNW of Northridge 6/2 5:13 am 34 18.1 116 50.5 2.0 2 mi. NNE of Big Bear City 6/2 5:30 am 35 7.5 115 23.8 2.2 39 mi. ESE of Baker 6/2 2:47 pm 35 18.1 119 53.4 2.5 7 mi. ESE of Simmler 6/2 4:06 pm 33 40.8 120 4.9 2.2 18 mi. S of Santa Rosa Is. 6/3 1:07 am 34 22.6 118 38.2 2.0 4 mi. WSW of Valencia 6/3 5:38 am 32 11.8 115 47.6 2.8 36 mi. SSW of Calexico 6/3 6:09 am 32 11.8 115 47.5 2.7 36 mi. SSW of Calexico 6/3 3:18 pm 33 56.6 117 47.9 2.4 3 mi. NNE of Yorba Linda 6/3 5:33 pm 32 55.5 116 17.0 2.1 17 mi. SSW of Ocotillo Wells 6/4 3:55 pm 33 28.6 116 31.1 2.9 10 mi. ESE of Anza -------------------------------------------------------------