September 1, 1994 Weekly Earthquake Report for Southern California ------------------------------------------------ August 25 - 31, 1994 Prepared by: Debbie Wells, Seismological Laboratory Nick Scheckel, 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, August 25, Pacific Daylight Time, to midnight Wednesday night, August 31, Pacific Daylight Time. We recorded 335 earthquakes this week. This week's activity was dominated, unsurprisingly, by Northridge and Landers aftershocks. The small swarm of Northridge aftershocks near Canoga Park continued this week, with it's largest event, a M3.3, occurring on Friday night. It showed a thrust focal mechanism, just like the rest of the Northridge sequence. This was felt by the public. Two other events were felt by the public this week, both of which were part of this Canoga Park swarm. One was a M2.8 on Friday evening and the other was a M3.1 on Saturday morning. Other events generated some media interest (a couple of M3.1 Landers aftershocks, one near Barstow and one near Yucca Valley, and a couple more Canoga Park events - M2.6 and M2.5), but apparently went unfelt by the public. The largest event of the week occurred early Sunday morning. It was a M3.5 outside of Baker and was the largest event in a small cluster of 10-15 events in that area. There were only a couple of events in each of the Fontana and Indio swarms. The table lists the quakes 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 ------------------------------------------------------------- 8/25 5:47 am 34 3.3 117 29.7 2.1 Fontana, 2 mi. ESE of the I10/I15 interchange 8/25 6:13 am 34 18.3 116 26.6 2.5 12 mi. N of Yucca Valley 8/25 6:16 am 34 3.3 117 29.8 2.0 Fontana, 2 mi. ESE of the I10/I15 interchange 8/25 9:57 am 34 5.5 116 26.4 2.1 1 mi. S of Yucca Valley 8/25 10:02 am 34 12.7 118 38.5 2.5 2 mi. WNW of Canoga Park 8/25 11:50 am 33 33.3 116 55.4 2.1 13 mi. SSE of Hemet 8/25 6:30 pm 34 10.5 116 49.6 2.4 5 mi. N of Mt. San Gorgonio 8/25 10:08 pm 35 32.7 116 5.4 2.3 19 mi. N of Baker 8/26 2:22 am 35 2.2 116 60.0 2.7 10 mi. N of Barstow 8/26 4:23 am 34 21.8 118 30.3 2.2 1 mi. SE of Newhall 8/26 5:57 am 35 21.2 118 37.0 2.0 15 mi. NE of Arvin 8/26 6:43 am 35 6.2 118 57.1 2.3 5 mi. N of the I5/99 interchange 8/26 10:42 am 34 54.4 116 55.2 3.1 5 mi. ENE of Barstow 8/26 11:28 am 34 1.4 117 9.1 2.0 2 mi. SE of Redlands 8/26 4:27 pm 33 48.0 116 58.0 2.7 3 mi. N of Hemet 8/26 5:28 pm 34 12.9 118 38.5 2.8 2 mi. WNW of Canoga Park; FELT 8/26 6:18 pm 34 56.0 119 4.1 2.0 8 mi. SW of the I5/99 interchange 8/26 9:12 pm 34 13.0 118 38.0 3.3 2 mi. NW of Canoga Park; FELT 8/26 9:16 pm 34 13.0 118 38.0 2.1 2 mi. NW of Canoga Park 8/26 9:28 pm 32 44.9 115 25.9 2.7 6 mi. NE of Calexico 8/26 10:23 pm 34 19.3 118 34.2 2.3 4 mi. SSW of Newhall 8/27 4:03 am 34 12.8 118 38.6 3.1 2 mi. WNW of Canoga Park; FELT 8/27 4:16 am 34 12.6 118 39.0 2.4 2 mi. WNW of Canoga Park 8/27 5:02 am 32 39.8 115 54.7 2.1 6 mi. SE of Ocotillo 8/27 3:50 pm 34 12.8 118 38.1 2.3 1 mi. WNW of Canoga Park 8/27 7:54 pm 34 12.6 118 38.4 2.1 2 mi. WNW of Canoga Park 8/28 1:05 am 34 13.0 118 38.4 2.3 " 8/28 1:17 am 34 15.7 118 27.1 2.4 1 mi. SSW of San Fernando 8/28 5:20 am 34 47.5 116 17.8 3.5 35 mi. SSW of Baker 8/28 5:50 am 34 46.1 116 16.9 2.0 " 8/28 6:40 am 34 47.4 116 17.6 2.0 " 8/28 3:30 pm 34 22.1 116 27.8 2.3 17 mi. N of Yucca Valley 8/28 10:09 pm 34 47.0 116 17.5 2.0 35 mi. SSW of Baker 8/28 10:28 pm 36 24.0 117 55.4 2.3 9 mi. NNE of Olancha 8/28 11:29 pm 35 52.3 118 25.6 2.2 16 mi. N of the town of Lake Isabella 8/29 2:47 am 33 51.5 118 45.5 2.0 10 mi. SSE of Pt. Dume 8/29 4:40 am 34 10.3 116 49.6 2.2 4 mi. N of Mt. San Gorgonio 8/29 9:56 am 33 48.6 116 11.8 2.2 6 mi. N of Indio 8/29 11:20 am 34 12.5 118 38.6 2.2 2 mi. WNW of Canoga Park 8/29 3:01 pm 34 13.1 118 38.7 2.5 " 8/29 4:03 pm 34 12.9 118 39.3 2.0 " 8/29 4:55 pm 34 46.9 116 17.8 2.0 35 mi. SSW of Baker 8/29 7:40 pm 34 5.1 116 58.9 2.5 8 mi. W of Mt. San Gorgonio 8/29 11:43 pm 32 1.4 117 12.8 2.4 37 mi. SSW of San Ysidro 8/30 2:12 am 32 49.8 115 38.4 2.0 5 mi. WNW of El Centro 8/30 3:40 am 33 48.7 116 12.0 2.4 6 mi. N of Indio 8/30 4:59 am 35 43.9 118 4.2 2.0 22 mi. SSW of Coso Junction 8/30 7:58 am 34 16.4 118 36.0 2.2 5 mi. N of Canoga Park 8/30 8:59 am 34 9.0 116 25.7 2.9 2 mi. NNE of Yucca Valley 8/30 3:06 pm 32 7.2 116 25.6 2.7 46 mi. SE of San Ysidro 8/30 4:02 pm 36 8.6 118 14.6 2.0 16 mi. SW of Olancha 8/30 9:09 pm 34 57.4 116 49.6 2.2 12 mi. ENE of Barstow 8/31 11:54 am 36 28.7 117 56.0 2.0 11 mi. SE of Lone Pine 8/31 12:40 pm 33 21.7 116 18.0 2.3 8 mi. NNE of Borrego Springs 8/31 2:20 pm 32 26.7 115 14.4 2.0 21 mi. SE of Calexico 8/31 7:09 pm 32 46.4 115 33.2 2.0 1 mi. S of El Centro 8/31 10:14 pm 36 0.6 117 48.9 2.1 7 mi. ESE of Coso Junction 8/31 11:10 pm 34 4.0 116 54.1 2.0 4 mi. WSW of Mt. San Gorgonio ------------------------------------------------------------- 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.