October 28, 1993 Weekly Earthquake Report for Southern California ------------------------------------------------ October 21 - October 27, 1993 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 21, Pacific Daylight Time, to midnight Wednesday night, October 27, Pacific Daylight Time. The map includes a virtually complete set of earthquakes of M2.0 or larger, plus many smaller ones that happen to have made it through the data processing. There are 425 this time. Quakes occurred at two different locations along the eastern front of the Sierra Nevada this week. The largest were a M3.9 at 7:37 am last Thursday, and a M3.7 at 9:30 am on Friday, at different locations. Both sites also experienced some smaller quakes and have been the site of similar swarms in the past. None of these quakes produced much public interest. There were also some quakes in the area east of Barstow: a M3.5 at 5:18 pm on Sunday and a M3.9 at 2:24 am on Tuesday. Both these were felt. These two quakes, along with the usual Barstow activity associated with the Landers aftershock zone, seem to mark an east-west trend on the map. Slightly farther to the east, there is an east-west trending fault (the Manix fault) mapped. However, the mechanism of the Sunday afternoon quake does not have any east-west planes, so the trend may not be real. We will be looking into these earthquakes a bit further. The Magic Mountain quake on Thursday morning also produced some public interest; it was M3.2 and was felt. The table lists the quakes that were M2.0 or larger in the central part of the coverage area. Only M2.5 and larger events are listed for south of the U.S./Mexico border, and for the Coalinga/Parkfield area. For more information on the latter, see the Northern California Report issued by the U.S.G.S. in Menlo Park. Times are local times; if you want Greenwich Mean Time, add 7 hrs. to the Pacific Daylight Time listed. Table 1 ------- Date Time N Lat. W Long. Mag ------------------------------------------------------------- 10/21 7:09 am 32 40.3 115 54.9 2.1 6 mi. SE of Ocotillo 10/21 7:37 am 36 9.3 118 2.0 3.9 Sierra foothills, 5 mi. W of Haiwee Reservoir 10/21 7:42 am 36 9.4 118 2.3 2.2 " 10/21 7:45 am 36 9.7 118 1.9 2.9 " 10/21 7:46 am 36 9.7 118 2.0 2.6 " 10/21 9:09 am 34 6.2 116 59.8 2.4 9 mi. SE of Running Springs 10/21 9:22 am 34 24.9 118 34.2 3.2 1 mi. ESE of Magic Mtn.; FELT 10/21 9:34 am 36 9.3 118 2.2 2.1 5 mi. W of Haiwee Reservoir 10/21 10:17 am 32 40.2 115 54.5 2.2 6 mi. SE of Ocotillo 10/21 10:23 am 34 58.2 116 57.7 2.7 6 mi. NNE of Barstow 10/21 11:14 am 32 38.2 118 5.7 2.3 19 mi. SE of San Clemente Is. 10/21 12:49 pm 34 6.2 116 59.9 2.1 9 mi. SE of Running Springs 10/21 1:54 pm 36 8.5 118 2.9 2.5 5 mi. W of Haiwee Reservoir 10/21 5:15 pm 36 9.1 118 2.0 2.3 " 10/21 5:38 pm 35 0.3 116 58.1 2.3 8 mi. NNE of Barstow 10/21 6:08 pm 34 9.0 116 25.2 2.2 2 mi. NNE of Yucca Valley 10/21 6:42 pm 32 25.5 115 2.5 2.5 35 mi. SE of Calexico 10/21 8:38 pm 33 57.9 117 11.4 2.3 6 mi. S of Redlands 10/21 8:38 pm 36 55.0 117 45.9 2.4 Saline Range, 27 mi. NE of Lone Pine 10/21 9:39 pm 34 2.0 116 49.7 2.8 4 mi. S of Mt. San Gorgonio 10/21 10:00 pm 34 9.2 116 24.9 2.4 2 mi. NE of Yucca Valley 10/22 1:28 am 34 2.8 119 13.6 2.4 6 mi. S of Port Hueneme 10/22 5:40 am 34 8.8 116 26.0 2.2 2 mi. NNE of Yucca Valley 10/22 6:35 am 35 46.2 115 58.5 2.3 Kingston Range, 21 mi. SE of Shoshone 10/22 6:59 am 34 26.0 116 30.8 2.0 22 mi. N of Yucca Valley 10/22 7:11 am 34 35.8 116 37.1 2.5 21 mi. ENE of Lucerne Valley 10/22 9:30 am 36 3.3 117 58.1 3.7 Sierra foothills, 1 mi. WNW of Coso Junction 10/22 10:06 am 36 3.1 117 57.8 3.1 " 10/22 10:25 am 34 20.8 116 27.7 2.4 15 mi. N of Yucca Valley 10/22 10:33 am 36 3.3 117 58.1 3.0 1 mi. WNW of Coso Junction 10/22 5:54 pm 36 3.2 117 58.0 2.0 " 10/22 6:10 pm 34 16.8 116 41.2 2.0 9 mi. E of Big Bear City 10/22 9:44 pm 34 58.2 116 57.8 3.1 6 mi. NNE of Barstow 10/23 12:51 am 34 56.8 116 46.5 2.2 14 mi. ENE of Barstow 10/23 2:49 am 34 20.6 116 27.5 2.4 15 mi. N of Yucca Valley 10/23 3:11 am 36 3.3 117 58.3 2.6 1 mi. WNW of Coso Junction 10/23 3:58 am 34 48.6 120 58.2 2.2 24 mi. NW of Pt. Arguello 10/23 8:44 am 35 18.1 118 34.7 2.3 13 mi. NNW of Tehachapi 10/23 12:03 pm 36 3.2 117 58.0 3.2 1 mi. WNW of Coso Junction 10/23 11:50 pm 34 58.9 116 58.5 2.1 7 mi. NNE of Barstow 10/24 1:33 am 34 6.1 116 59.7 2.3 9 mi. SE of Running Springs 10/24 4:05 am 32 45.2 117 24.3 2.1 11 mi. SW of La Jolla 10/24 4:42 am 34 37.3 116 37.4 2.0 22 mi. NE of Lucerne Valley 10/24 7:07 am 34 0.8 117 6.3 2.0 4 mi. SE of Redlands 10/24 9:28 am 36 3.2 117 58.3 2.0 1 mi. WNW of Coso Junction 10/24 9:48 am 32 19.2 115 3.9 2.8 34 mi. SE of Calexico 10/24 1:02 pm 32 20.4 115 3.3 2.6 " 10/24 5:18 pm 34 56.5 116 47.4 3.5 13 mi. ENE of Barstow; FELT 10/24 5:52 pm 34 56.4 116 47.4 2.0 13 mi. ENE of Barstow 10/24 6:09 pm 34 56.7 116 39.5 2.2 21 mi. E of Barstow 10/24 7:58 pm 36 9.2 118 2.5 2.1 5 mi. WNW of south end of Haiwee Reservoir 10/24 8:45 pm 34 22.2 116 26.2 2.1 17 mi. N of Yucca Valley 10/24 10:08 pm 34 56.6 116 47.3 2.4 13 mi. ENE of Barstow 10/25 1:42 am 34 57.6 116 58.6 2.8 5 mi. NNE of Barstow 10/25 2:47 am 33 0.6 116 33.9 2.3 5 mi. SSE of Julian; FELT 10/25 4:02 am 33 0.4 116 34.2 2.6 " FELT 10/25 6:45 am 32 20.4 115 4.1 2.6 33 mi. SE of Calexico 10/25 7:05 am 33 41.8 118 0.4 2.2 6 mi. ESE of Seal Beach 10/25 10:22 am 35 22.9 118 29.8 2.1 17 mi. S of the town of Lake Isabella 10/25 5:12 pm 34 38.0 116 39.2 2.0 21 mi. NE of Lucerne Valley 10/25 7:17 pm 36 9.0 120 5.5 2.7 14 mi. E of Coalinga 10/25 9:28 pm 32 18.3 115 3.9 2.5 35 mi. SE of Calexico 10/25 9:28 pm 32 14.9 114 58.2 3.0 37 mi. SSW of Yuma, Arizona 10/25 9:30 pm 32 19.4 115 3.7 2.6 34 mi. SE of Calexico 10/25 9:51 pm 36 15.5 120 48.9 3.0 26 mi. WNW of Coalinga 10/25 9:51 pm 34 55.8 116 55.7 3.0 6 mi. ENE of Barstow; FELT 10/25 11:25 pm 34 55.9 116 56.0 2.0 " 10/26 1:59 am 33 16.9 116 26.8 2.4 4 mi. WNW of Borrego Springs 10/26 2:24 am 34 56.8 116 39.1 3.9 21 mi. E of Barstow; FELT 10/26 3:37 am 33 11.6 115 33.9 2.8 4 mi. SW of Niland 10/26 4:11 am 32 20.2 115 3.8 2.5 33 mi. SE of Calexico 10/26 6:39 am 34 55.2 116 55.0 2.3 6 mi. ENE of Barstow 10/26 6:57 am 32 19.9 115 3.5 2.8 34 mi. SE of Calexico 10/26 6:57 am 32 19.0 115 4.6 3.0 " 10/26 7:22 am 34 25.5 116 32.1 2.0 21 mi. NNW of Yucca Valley 10/26 5:34 pm 34 23.4 116 27.5 2.0 18 mi. N of Yucca Valley 10/26 10:45 pm 33 31.4 116 34.3 2.6 6 mi. ESE of Anza 10/26 11:00 pm 34 11.8 116 25.8 2.0 5 mi. N of Yucca Valley 10/26 11:48 pm 36 9.7 118 1.5 2.3 4 mi. WNW of south end of Haiwee Reservoir 10/27 2:51 am 34 8.7 116 25.0 2.8 2 mi. NE of Yucca Valley 10/27 9:14 am 34 23.0 116 27.2 2.2 18 mi. N of Yucca Valley 10/27 11:04 am 34 56.8 116 39.4 2.4 21 mi. E of Barstow 10/27 12:22 pm 35 18.4 118 33.1 2.4 13 mi. NNW of Tehachapi 10/27 5:09 pm 35 13.8 118 4.6 3.4 13 mi. NNE of Mojave 10/27 6:29 pm 34 36.6 116 37.0 2.0 21 mi. ENE of Lucerne Valley 10/27 10:16 pm 36 49.4 116 22.2 2.4 37 mi. NE of Furnace Creek, Death Valley 10/27 11:52 pm 33 51.8 118 26.8 2.1 2 mi. SW of Manhattan Beach ------------------------------------------------------------- Figure. 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.