December 9, 1993 Weekly Earthquake Report for Southern California ------------------------------------------------ December 2 - 8, 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, December 2, Pacific Standard Time, to midnight Wednesday night, December 8, Pacific Standard 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 359 this time. A few earthquakes were felt by the public this week, the largest one being a M3.7 in the Big Bear area last Thursday afternoon. Another felt quake of some interest was the M2.9 Newhall quake on Friday morning. Although it looks a lot like an aftershock of the 1971 earthquake, we are not calling it such because the aftershock sequence died almost to nothing a decade ago. Note that both the quakes in the Los Angeles Basin were M2.1, too small to be felt. Most of the seismological excitement, however, did not prompt much public interest, since the bulk of it occurred south of the U.S./Mexican border. A healthy swarm has been going on there since late Tuesday, with the largest events being in the lower M3 range. Also notice the small quakes at Bombay Beach on Monday, largest M2.6. These quakes look as if they are in the Brawley Seismic Zone and not on the San Andreas, but they are just about as close to the southern end of the locked Coachella Valley segment of the San Andreas as quakes get. They were too small to produce much worry, however. 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 8 hrs, to the Pacific Standard Time listed. Table 1 ------- Date Time N Lat. W Long. Mag ------------------------------------------------------------- 12/2 6:52 am 32 14.4 115 44.4 2.6 32 mi. SSW of Calexico 12/2 11:31 am 35 54.7 117 43.7 2.7 15 mi. SE of Coso Junction 12/2 11:53 am 35 54.6 117 43.6 2.6 " 12/2 12:17 pm 35 54.6 117 43.7 2.2 " 12/2 2:32 pm 34 22.7 116 27.9 2.1 17 mi. N of Yucca Valley 12/2 4:17 pm 34 29.4 116 30.5 2.2 25 mi. N of Yucca Valley 12/2 4:18 pm 34 20.1 116 27.8 2.4 15 mi. N of Yucca Valley 12/2 4:34 pm 34 49.7 120 25.5 2.7 8 mi. S of Santa Maria; FELT 12/2 5:30 pm 35 1.5 116 58.2 2.0 9 mi. NNE of Barstow 12/2 5:51 pm 34 15.6 116 43.3 3.7 7 mi. E of Big Bear City; FELT 12/2 11:26 pm 34 49.0 120 24.5 2.0 9 mi. S of Santa Maria 12/3 4:31 am 33 57.7 118 19.1 2.1 1 mi. NE of Hollywood Park Racetrack 12/3 9:44 am 34 24.3 118 24.1 2.9 7 mi. ENE of Newhall; FELT 12/3 1:41 pm 34 38.2 116 32.5 2.3 26 mi. ENE of Lucerne Valley 12/3 2:00 pm 34 23.7 116 27.9 2.1 19 mi. N of Yucca Valley 12/3 3:11 pm 35 18.5 118 36.1 2.7 15 mi. NW of Tehachapi 12/3 5:36 pm 34 20.1 116 28.5 2.1 15 mi. N of Yucca Valley 12/3 6:13 pm 34 0.0 116 19.4 2.3 10 mi. SE of Yucca Valley 12/3 7:08 pm 32 56.1 117 37.6 2.2 22 mi. SW of Oceanside 12/3 8:12 pm 34 0.6 116 19.3 2.0 10 mi. SE of Yucca Valley 12/3 8:41 pm 34 37.7 116 35.3 2.4 24 mi. ENE of Lucerne Valley 12/4 8:27 am 34 29.4 116 30.6 2.1 25 mi. N of Yucca Valley 12/4 9:05 am 34 20.0 116 27.2 2.0 14 mi. N of Yucca Valley 12/4 10:59 am 35 0.6 116 57.9 2.6 9 mi. NNE of Barstow 12/4 12:27 pm 36 0.5 120 32.9 2.5 9 mi. NW of Parkfield 12/4 8:51 pm 34 37.2 116 39.8 2.2 20 mi. NE of Lucerne Valley 12/5 9:14 am 34 33.7 116 33.4 2.1 23 mi. ENE of Lucerne Valley 12/5 11:51 am 35 16.9 116 51.2 2.6 5 mi. SSE of Goldstone (dry) Lake 12/5 2:48 pm 34 13.1 117 36.0 2.0 5 mi. SSE of Mt. Baldy 12/5 2:55 pm 34 59.1 116 56.9 2.1 7 mi. NNE of Barstow 12/5 4:45 pm 34 10.3 116 26.4 2.1 3 mi. N of Yucca Valley 12/5 7:18 pm 36 3.2 117 58.1 2.4 1 mi. WNW of Coso Junction 12/5 11:03 pm 35 17.2 116 51.2 2.9 4 mi. SSE of Goldstone (dry) Lake 12/6 1:16 am 34 57.8 116 56.4 2.0 6 mi. NE of Barstow 12/6 1:27 am 35 4.2 116 39.4 2.5 23 mi. SSE of Goldstone (dry) Lake 12/6 2:53 am 34 58.8 116 56.8 2.3 7 mi. NE of Barstow 12/6 2:57 am 34 39.1 116 1.4 2.0 35 mi. N of Twentynine Palms 12/6 5:45 am 34 8.9 116 43.4 2.2 6 mi. ENE of Mt. San Gorgonio 12/6 12:50 pm 33 19.8 115 44.5 2.6 1 mi. SSW of Bombay Beach 12/6 12:52 pm 33 19.3 115 44.5 2.1 " 12/6 6:46 pm 33 21.5 116 22.0 2.0 7 mi. N of Borrego Springs 12/6 7:38 pm 33 23.3 116 53.8 2.2 2 mi. NW of Palomar Observatory 12/6 8:03 pm 33 48.1 118 19.4 2.1 4 mi. SSW of the I110/I405 interchange, Torrance 12/6 9:32 pm 35 17.5 116 51.1 2.5 4 mi. SSE of Goldstone (dry) Lake 12/7 10:57 am 34 7.3 116 23.1 2.3 3 mi. E of Yucca Valley 12/7 12:07 pm 34 8.4 116 58.3 2.8 7 mi. SSW of town of Big Bear Lake 12/7 2:22 pm 32 43.7 118 8.7 2.5 13 mi. ESE of San Clemente Is. 12/7 6:49 pm 32 21.4 115 21.2 3.4 24 mi. SSE of Calexico 12/7 6:52 pm 32 21.2 115 20.9 2.9 " 12/7 6:54 pm 32 20.6 115 20.9 2.6 " 12/7 7:02 pm 32 21.5 115 21.3 3.2 " 12/7 7:06 pm 32 18.2 115 21.5 3.2 " 12/7 7:10 pm 32 20.4 115 20.9 3.0 " 12/7 7:10 pm 32 18.1 115 21.2 3.2 " 12/7 7:17 pm 32 19.6 115 21.6 2.9 " 12/7 7:25 pm 32 21.1 115 20.7 3.0 " 12/7 8:27 pm 32 20.2 115 20.9 2.5 " 12/7 8:31 pm 32 19.5 115 20.9 2.8 " 12/7 8:32 pm 32 19.2 115 21.0 3.0 " 12/7 8:37 pm 32 20.9 115 20.7 2.5 " 12/7 9:00 pm 32 20.5 115 21.6 3.0 " 12/7 9:45 pm 33 35.6 118 17.8 2.2 7 mi. S of Pt. Fermin, San Pedro 12/7 10:11 pm 32 17.8 115 20.4 2.5 24 mi. SSE of Calexico 12/7 11:31 pm 32 14.7 115 19.4 2.9 " 12/8 12:47 am 32 20.2 115 21.4 3.3 " 12/8 1:06 am 35 0.5 116 58.0 3.6 8 mi. NNE of Barstow 12/8 1:47 am 32 20.4 115 21.1 2.8 24 mi. SSE of Calexico 12/8 2:30 am 32 19.8 115 14.9 2.8 " 12/8 3:58 am 35 0.1 116 57.2 2.1 8 mi. NNE of Barstow 12/8 5:09 am 34 59.2 116 56.8 2.7 " 12/8 5:25 am 32 21.5 115 21.3 2.6 24 mi. SSE of Calexico 12/8 6:56 am 34 11.7 116 47.9 2.3 5 mi. SSE of Big Bear City 12/8 12:02 pm 32 20.6 115 21.0 2.8 24 mi. SSE of Calexico 12/8 1:10 pm 33 34.0 118 16.3 2.6 9 mi. S of Pt. Fermin, San Pedro 12/8 4:07 pm 32 21.6 115 20.9 3.1 24 mi. SSE of Calexico 12/8 4:07 pm 32 22.0 115 21.0 3.4 " 12/8 7:16 pm 34 9.5 116 25.2 2.3 3 mi. NNE of Yucca Valley 12/8 7:25 pm 34 9.6 116 25.3 2.5 " 12/8 8:18 pm 32 22.0 115 21.4 3.1 24 mi. SSE of Calexico ------------------------------------------------------------- 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.