February 24, 1994 Weekly Earthquake Report for Southern California ------------------------------------------------ February 17 - 23, 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, February 17, Pacific Standard Time, to midnight Wednesday night, February 23, Pacific Standard Time. There are 561 this week. This is the first week since the Northridge earthquake, almost 6 weeks ago, that we have actually finished all the data processing. All of the events that you see have been inspected by one of our analysts. The week's largest event was the M3.7 early Friday morning near Northridge. There was a M3.2 near San Fernando later the same morning. Barstow had a M3.1 at 4:33 pm the same day. Coalinga experienced a M3.6 on Tuesday night. An interesting group of earthquakes occurred this week in Ventura Co. All 10 were small (M1.4 - M1.9), but they were distributed along a 50-km long lineation parallel to east-striking Ventura Basin. A line of events like this suggests geophyical blasting to us. However, these events had normal depths (between 2 and 16 km), making it unlikely that they were actually explosions rather than earthquakes. We have no obvious explanation for the lineation, and it will be interesting to see if the events continue into next week. The table lists the quakes that were M2.0 or larger in the central part of the coverage area. Aftershocks must be at least M2.5 to be listed. 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 ------------------------------------------------------------- 2/17 12:27 am 34 19.8 116 27.3 2.0 14 mi. N of Yucca Valley 2/17 7:11 am 34 19.0 118 27.3 2.5 2 mi. NNW of San Fernando 2/17 8:13 am 33 56.9 118 37.8 2.7 6 mi. SSE of Malibu 2/17 3:51 pm 36 9.1 118 2.0 2.4 5 mi. WNW of Haiwee Reservoir 2/17 9:04 pm 34 9.4 116 25.5 2.1 2 mi. NNE of Yucca Valley 2/17 9:26 pm 34 8.4 116 26.4 2.0 " 2/17 11:23 pm 33 59.7 116 33.7 2.1 4 mi. NW of Desert Hot Springs 2/18 1:13 am 34 14.1 118 34.5 3.7 2 mi. W of Northridge; FELT 2/18 1:52 am 36 9.1 118 1.9 2.3 4 mi. WNW of Haiwee Reservoir 2/18 2:56 am 34 32.5 116 35.9 2.1 20 mi. ENE of Lucerne Valley 2/18 7:44 am 34 18.1 118 27.2 3.2 1 mi. NNW of San Fernando FELT 2/18 9:05 am 34 13.4 116 45.9 2.1 5 mi. ESE of Big Bear City 2/18 3:01 pm 34 20.3 116 53.3 2.0 5 mi. NNW of Big Bear City 2/18 3:38 pm 35 21.3 117 37.7 2.1 18 mi. S of Ridgecrest 2/18 4:33 pm 34 59.1 116 56.7 3.1 8 mi. NE of Barstow 2/18 6:18 pm 34 37.0 116 40.3 2.0 19 mi. NE of Lucerne Valley 2/18 6:54 pm 34 14.5 118 28.5 2.8 3 mi. SW of San Fernando 2/19 12:28 am 34 15.8 118 33.2 2.5 2 mi. NNW of Northridge 2/19 7:55 am 34 0.6 116 18.3 2.5 10 mi. SE of Yucca Valley 2/19 9:17 am 34 19.0 118 34.5 2.5 5 mi. SSW of Newhall 2/19 9:24 pm 34 18.9 118 34.9 2.6 " 2/19 9:47 pm 34 0.2 117 12.6 2.3 4 mi. SSW of Redlands 2/19 11:50 pm 36 56.1 118 17.4 2.1 10 mi. NNW of Independence 2/20 3:44 am 33 56.9 116 19.8 2.0 9 mi. E of Desert Hot Springs 2/20 5:46 am 35 32.5 117 30.3 2.6 10 mi. ESE of Ridgecrest 2/20 7:03 am 34 17.9 118 27.2 2.5 1 mi. NW of San Fernando 2/20 11:27 am 34 26.0 119 52.7 2.8 2 mi. NW of Isla Vista 2/20 3:20 pm 34 1.1 116 26.1 2.4 5 mi. NE of Desert Hot Springs 2/21 7:04 am 34 22.3 118 37.9 2.5 4 mi. SW of Magic Mtn. 2/21 9:10 am 34 0.6 116 19.0 2.0 10 mi. SE of Yucca Valley 2/21 9:48 am 33 57.2 119 11.3 2.2 13 mi. S of Port Hueneme 2/21 10:12 am 34 6.3 116 24.3 2.0 2 mi. ESE of Yucca Valley 2/21 8:49 pm 34 16.9 116 50.7 2.3 1 mi. NNE of Big Bear City 2/22 1:48 am 34 15.6 118 33.0 2.6 1 mi. NNW of Northridge 2/22 3:37 am 34 9.4 116 25.5 2.1 2 mi. NNE of Yucca Valley 2/22 5:57 am 34 34.1 116 33.4 2.8 23 mi. ENE of Lucerne Valley 2/22 1:02 pm 34 20.1 118 45.9 2.9 5 mi. NW of Simi Valley 2/22 1:46 pm 34 12.8 118 35.8 2.5 Under Canoga Park 2/22 6:57 pm 34 57.4 116 47.3 2.1 14 mi. ENE of Barstow 2/22 7:44 pm 34 0.5 116 19.8 2.5 10 mi. SE of Yucca Valley 2/22 7:58 pm 34 57.4 116 47.4 2.8 14 mi. ENE of Barstow 2/22 10:20 pm 34 2.4 116 23.3 2.3 6 mi. SSE of Yucca Valley 2/22 10:58 pm 36 17.5 120 15.2 3.6 12 mi. NNE of Coalinga 2/23 3:23 am 34 18.5 118 27.0 2.5 1 mi. NNW of San Fernando 2/23 5:40 am 34 20.1 116 28.4 2.2 15 mi. N of Yucca Valley 2/23 9:57 am 34 16.3 118 33.5 2.5 2 mi. NNW of Northridge 2/23 3:24 pm 33 38.5 118 26.6 2.0 9 mi. S of Palos Verdes Point 2/23 3:58 pm 34 1.6 117 2.7 2.3 7 mi. NNW of Beaumont 2/23 6:54 pm 34 18.1 118 26.4 2.9 1 mi. N of San Fernando ------------------------------------------------------------- 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.