October 27, 1994 Weekly Earthquake Report for Southern California ------------------------------------------------ October 20 - 26, 1994 Prepared by: Kate Hutton, Seismological Laboratory (kate@bombay.gps.caltech.edu) Lucy Jones, U.S. Geological Survey California Institute of Technology This document is a commentary on current seismic activity. The earthquakes discussed have been detected and processed automatically. All epicenters and magnitudes have been reviewed to exclude obvious blunders; however, they must still be considered preliminary. For further information, please contact the authors or the Caltech Public Relations Office at 818-395-6326. For daily updates, call our Earthquake Information Hotline: 818-395-6977. -------------------------------- This week's Report covers the time period from midnight Thursday morning, October 20, Pacific Daylight Time, to midnight Wednesday night, October 26, Pacific Daylight Time. We recorded 387 earthquakes of M1.0 or larger this week. We experienced an upsurge in activity this week, compared to the last couple of weeks. This is probably not, however, beyond the range expected statistically. No single are was responsible for the increase, and no events exceeded M4. After- shocks in the two major sequences (Landers and Northridge) continued to dominate the map. The largest quake was a M3.4 that was part of a cluster in the Death Valley region, on Sunday. The M3.4 occurred near the tail end of the cluster, in the evening. The second largest event was a M3.3 in the southern San Joaquin Valley, early last Friday morning. There was also a M3.1 SE of Ridgecrest on Sunday evening. It was part of a swarm that continued from last week. That swarm produced a M4.3 last week. Another M3.1, on Monday morning, was a Landers aftershock and was felt in Yucca Valley. The table 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 Daylight Time listed. Table 1 ------- Date Time N Lat. W Long. Mag ------------------------------------------------------------- 10/20 5:05 am 34 17.0 116 23.4 2.4 11 mi. NNE of Yucca Valley 10/20 5:28 am 32 40.4 115 54.5 2.1 6 mi. SE of Ocotillo 10/20 10:10 am 33 45.2 118 23.6 2.0 2 mi. SE of Palos Verdes Point 10/20 12:19 pm 35 8.1 117 19.3 2.5 24 mi. NW of Barstow 10/21 2:28 am 32 43.3 115 55.2 2.0 4 mi. ESE of Ocotillo 10/21 4:02 am 34 21.5 118 37.3 2.1 4 mi. SSW of Magic Mtn. 10/21 4:42 am 35 1.0 118 57.4 3.3 San Juaquin Valley, I5/99 interchange 10/21 4:52 am 35 0.7 118 57.1 2.2 " 10/21 6:23 am 34 10.6 116 49.6 2.0 5 mi. N of Mt. San Gorgonio 10/21 7:31 pm 35 30.6 117 29.6 2.1 12 mi. SE of Ridgecrest 10/21 11:05 pm 35 23.9 117 49.6 2.3 17 mi. SSW of Ridgecrest 10/22 12:15 am 34 25.0 116 28.7 2.2 20 mi. N of Yucca Valley 10/22 7:00 am 34 20.7 116 53.8 2.2 6 mi. NNW of Big Bear City 10/22 7:26 am 32 17.2 115 7.3 2.8 34 mi. SE of Calexico 10/22 8:07 am 32 17.9 115 7.6 2.5 " 10/22 9:42 am 32 17.8 115 8.1 2.8 " 10/22 10:35 am 33 42.3 116 45.7 2.3 3 mi. SW of Idyllwild 10/22 10:35 am 33 42.6 116 45.8 2.0 " 10/22 9:23 pm 33 42.8 116 49.4 2.2 6 mi. WSW of Idyllwild 10/23 1:33 am 34 58.9 116 56.9 2.0 7 mi. NNE of Barstow 10/23 2:21 am 34 16.3 118 37.0 2.2 4 mi. N of Canoga Park 10/23 4:15 am 35 47.7 117 30.1 2.0 7 mi. WNW of Trona 10/23 7:58 am 34 22.6 116 27.8 2.5 17 mi. N of Yucca Valley 10/23 9:02 am 34 19.1 116 31.0 2.5 14 mi. NNW of Yucca Valley 10/23 10:38 am 35 50.2 116 51.4 2.0 Death Valley, 26 mi. SSE of Telescope Peak 10/23 10:47 am 35 51.0 116 51.3 2.4 " 10/23 11:05 am 35 50.3 116 52.0 2.9 " 10/23 12:36 pm 35 50.3 116 51.8 2.6 " 10/23 4:37 pm 34 48.9 118 54.8 2.0 1 mi. E of Frazier Park 10/23 6:22 pm 32 15.1 116 27.5 2.5 39 mi. ESE of San Ysidro 10/23 7:52 pm 35 49.9 116 52.1 3.4 Death Valley, 26 mi. SSE of Telescope Peak 10/23 8:17 pm 35 30.8 117 29.6 3.1 12 mi. SE of Ridgecrest 10/23 9:34 pm 33 58.5 117 48.6 2.4 6 mi. N of Yorba Linda 10/24 4:38 am 34 2.4 116 19.3 2.7 8 mi. SE of Yucca Valley 10/24 8:17 am 34 15.9 116 27.5 3.1 10 mi. N of Yucca Valley 10/24 8:46 am 34 8.8 116 24.5 2.0 2 mi. NE of Yucca Valley 10/24 10:23 am 34 47.1 116 17.7 2.0 35 mi. SSW of Baker 10/24 2:20 pm 35 30.7 117 29.7 2.8 12 mi. SE of Ridgecrest 10/24 2:26 pm 34 2.3 117 30.4 2.0 Fontana, 2 mi. SE of the I10/I15 interchange 10/24 5:35 pm 33 56.0 116 21.6 2.7 8 mi. ESE of Desert Hot Springs 10/24 7:47 pm 34 14.9 118 40.8 2.1 2 mi. SE of Simi Valley 10/24 7:52 pm 33 14.6 116 1.7 2.1 4 mi. SW of Salton City 10/24 9:02 pm 32 1.8 115 26.7 2.6 44 mi. S of Calexico 10/25 1:39 am 34 15.6 117 38.5 2.6 1 mi. SSE of Mt. Baldy 10/25 2:40 am 34 15.9 116 27.5 2.8 10 mi. N of Yucca Valley 10/25 5:48 am 36 11.9 120 45.9 2.9 22 mi. W of Coalinga 10/25 9:46 am 34 18.1 116 56.2 2.0 4 mi. NNW of town of Big Bear Lake 10/25 1:57 pm 34 48.3 116 18.7 2.1 34 mi. SSW of Baker 10/25 4:54 pm 34 10.0 118 41.1 2.3 5 mi. WSW of Canoga Park 10/25 9:14 pm 32 17.0 115 7.7 2.5 34 mi. SE of Calexico 10/25 9:18 pm 34 10.1 118 41.3 2.4 5 mi. WSW of Canoga Park 10/25 10:04 pm 33 15.6 116 50.4 2.0 4 mi. WNW of Lake Henshaw 10/25 11:24 pm 34 2.2 116 19.3 2.0 9 mi. SE of Yucca Valley 10/26 6:02 am 33 36.9 116 41.2 2.1 4 mi. N of Anza 10/26 6:14 am 35 59.8 117 24.2 2.3 16 mi. N of Trona 10/26 9:27 am 32 17.7 115 7.4 2.5 33 mi. SE of Calexico 10/26 11:13 am 32 17.0 115 7.8 2.5 " 10/26 12:00 pm 34 3.0 116 19.2 2.3 8 mi. ESE of Yucca Valley 10/26 3:54 pm 33 57.8 118 54.6 2.1 5 mi. SSE of Leo Carrillo State Beach 10/26 4:27 pm 33 46.4 116 8.4 2.6 5 mi. NE of Indio 10/26 4:39 pm 33 46.4 116 8.4 2.0 " ------------------------------------------------------------- Figure 1. A map of southern California showing the earthquakes recorded during the past week by the Caltech/USGS Seismic Network. Major faults are marked, as well as the metropolitan areas of Los Angeles (L.A.), Palm Springs (P.S.), San Diego (S.D.), and Santa Barbara (S.B.). The circles denote the earthquakes, the size of the circle indicating the magnitude.