April 28, 1994 Weekly Earthquake Report for Southern California ------------------------------------------------ April 21 - 27, 1994 Prepared by: Nick Scheckel & Debbie Wells, 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, April 21, Pacific Daylight Time, to midnight Wednesday night, April 27, Pacific Daylight Time. There are 382 this week. It was a fairly average week. There were four Northridge aftershocks felt by the public: a M3.0 on Sunday morning, a M3.0 and a M3.5 on Wednesday morning and a M2.5 on Wednesday night. The expected number of aftershocks above M3.0 for last week and next is 3 so this level of aftershocks is exactly average. The largest event of the week was a M4.4 near Coalinga on Thursday morning, followed a couple of hours later by a M3.4. For information on these events, contact the U.S. Geological Survey in Menlo Park, at 415-853-8300. Small earthquakes continued in the ordinary locations such as the San Jacinto fault, the LA basin and the Landers aftershock zone but none were large enough to be reported as felt this week. 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 ------------------------------------------------------------- 4/21 9:37 am 36 18.1 120 23.6 4.4 11 mi. N of Coalinga; FELT 4/21 11:05 am 36 18.4 120 21.0 3.4 " 4/21 11:43 am 35 19.0 117 39.2 2.2 21 mi. S of Ridgecrest 4/21 1:31 pm 34 18.1 118 32.8 2.0 4 mi. N of Northridge 4/21 7:33 pm 33 39.8 116 45.8 2.5 6 mi. SSW of Idyllwild 4/21 9:14 pm 34 38.4 116 33.3 2.1 26 mi. ENE of Lucerne Valley 4/22 5:07 am 35 43.8 117 35.2 2.0 8 mi. NNE of Ridgecrest 4/22 10:50 am 34 17.9 118 26.6 2.6 1 mi. NNW of San Fernando 4/22 1:15 pm 36 11.5 117 34.6 2.7 11 mi. SSW of Panamint Springs 4/22 2:08 pm 34 24.7 116 21.4 2.1 20 mi. NNE of Yucca Valley 4/22 3:07 pm 34 16.9 118 28.7 2.1 2 mi. W of San Fernando 4/22 5:20 pm 34 21.1 118 34.4 2.0 3 mi. SW of Newhall 4/22 6:57 pm 33 58.4 116 58.8 2.7 3 mi. N of Beaumont 4/23 12:12 am 34 24.4 116 28.2 2.3 19 mi. N of Yucca Valley 4/23 12:43 am 33 12.8 116 3.4 2.2 6 mi. NE of Ocotillo Wells 4/23 7:15 am 34 16.1 118 42.1 2.8 Under Simi Valley 4/23 12:29 pm 34 59.5 116 57.2 2.0 8 mi. NNE of Barstow 4/23 1:36 pm 34 23.3 116 27.5 2.1 18 mi. N of Yucca Valley 4/23 5:57 pm 34 15.6 118 35.5 2.2 4 mi. N of Canoga Park 4/23 10:00 pm 35 18.8 117 38.9 2.0 21 mi. S of Ridgecrest 4/23 10:23 pm 34 0.8 116 19.2 2.3 10 mi. SE of Yucca Valley 4/24 12:05 am 35 18.7 117 39.1 2.2 21 mi. S of Ridgecrest 4/24 12:05 am 34 19.4 118 36.0 2.4 5 mi. SW of Newhall 4/24 1:57 am 34 21.0 118 42.1 2.1 4 mi. N of Simi Valley 4/24 2:03 am 34 20.2 116 28.1 2.4 15 mi. N of Yucca Valley 4/24 4:00 am 34 23.4 118 46.7 2.2 8 mi. NNW of Simi Valley 4/24 4:00 am 34 16.5 118 27.6 2.0 1 mi. WSW of San Fernando 4/24 5:04 am 34 36.9 116 35.7 2.1 23 mi. ENE of Lucerne Valley 4/24 8:54 am 34 18.5 118 37.1 3.0 5 mi. ENE of Simi Valley; FELT 4/24 10:52 am 34 22.1 118 30.3 2.1 1 mi. ESE of Newhall 4/24 12:08 pm 34 19.6 118 30.8 2.7 3 mi. SSE of Newhall 4/24 6:55 pm 34 1.0 118 21.3 2.0 1 mi. NE of Baldwin Hills 4/24 7:47 pm 34 6.1 116 49.9 2.5 Under Mt. San Gorgonio 4/25 2:30 am 34 31.7 118 47.7 2.3 11 mi. NE of Fillmore 4/25 4:13 am 34 12.6 118 35.3 2.1 1 mi. NE of Canoga Park 4/25 8:42 am 34 13.3 116 45.2 2.0 6 mi. ESE of Big Bear City 4/25 11:21 pm 34 29.1 116 30.9 2.2 25 mi. N of Yucca Valley 4/26 1:02 am 34 15.7 116 26.1 2.2 9 mi. N of Yucca Valley 4/26 3:06 am 33 59.4 118 20.4 2.5 2 mi. ESE of Baldwin Hills 4/26 5:42 am 34 15.4 118 31.3 2.4 1 mi. NNE of Northridge 4/26 6:26 am 33 57.2 119 27.8 2.0 6 mi. SSE of Santa Cruz Is. 4/26 9:23 am 36 0.4 117 26.0 2.6 16 mi. NNW of Trona 4/26 9:42 am 34 20.7 116 25.7 2.6 15 mi. N of Yucca Valley 4/26 11:24 am 34 14.0 118 34.3 2.0 2 mi. W of Northridge 4/26 3:35 pm 33 13.4 116 2.6 2.1 5 mi. SW of Salton City 4/26 3:35 pm 34 17.7 118 24.3 2.2 2 mi. ENE of San Fernando 4/26 7:45 pm 34 22.8 118 33.9 2.3 2 mi. W of Newhall 4/26 8:29 pm 34 27.0 116 28.0 2.0 22 mi. N of Yucca Valley 4/27 2:39 am 34 18.5 118 36.9 3.0 5 mi. ENE of Simi Valley; FELT 4/27 5:11 am 34 21.9 118 36.9 2.4 4 mi. SSW of Magic Mtn. 4/27 5:20 am 34 22.0 118 36.5 2.1 " 4/27 5:33 am 34 14.9 118 44.7 3.5 2 mi. SW of Simi Valley; FELT 4/27 5:44 am 34 14.9 118 45.3 2.5 " 4/27 7:21 am 33 17.7 116 14.5 2.2 8 mi. ENE of Borrego Springs 4/27 12:03 pm 34 15.6 118 27.9 2.2 2 mi. SW of San Fernando 4/27 3:18 pm 34 14.5 118 30.5 2.0 1 mi. ENE of Northridge 4/27 3:18 pm 33 56.0 116 23.1 2.0 7 mi. ESE of Desert Hot Springs 4/27 4:43 pm 34 49.1 116 42.3 2.0 18 mi. ESE of Barstow 4/27 5:57 pm 36 1.2 117 24.7 2.0 17 mi. N of Trona 4/27 6:44 pm 34 10.5 116 26.0 2.1 3 mi. N of Yucca Valley 4/27 10:31 pm 34 17.4 118 28.6 2.5 2 mi. WNW of San Fernando; FELT ------------------------------------------------------------- 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.