SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey March 30, 1995 Weekly Earthquake Report for Southern California ------------------------------------------------ March 23 - 29, 1995 Prepared by: Kate Hutton, Seismological Laboratory (kate@bombay.gps.caltech.edu) Lucy Jones, U.S. Geological Survey California Institute of Technology 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, March 23, Pacific Standard Time, to midnight Wednesday night, March 29, 1995, Pacific Standard Time. We recorded 288 earthquakes of M1.0 or larger during the 7-day period covered. Although the total number of events this week was almost the same as past weeks, there were a number of felt and potentially feelable quakes. This variation is statistically expected, by the way. Rather like throwing five "heads" in a row while tossing coins; it's not common, but it does happen occasionally. Two Northridge aftershocks, a M3.0 on Friday evening and a M2.6 on Saturday afternoon, were both felt in the San Fernando area. The focal mechanism of the M3.0 was what we have come to expect from the Northridge aftershock zone: thrust on an east- striking fault. Also, a Lander/Big Bear aftershock (M2.8) was felt in the Big Bear area on Sunday afternoon. On Monday morning, a M3.3 was felt in the Desert Hot Springs area. This quake was located a few miles west of the Landers aftershock zone, and is not considered an aftershock. It occurred on a north-striking normal fault. We commonly see clusters of small, normal-faulting earthquakes in this region. They are thought to be associated with the many small normal faults of the Little San Bernardino Mountains. There were three other M3+ events that apparently went unnoticed by the public. These were: a M3.0 on Sunday afternoon in the Grapevine area, a M3.0 Landers aftershock (with the expected strike-slip mechanism) late Sunday night, and a M3.2 just before noon on Tuesday, just south of the U.S./Mexican border. The table lists the quakes this week 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 Pacific Daylight Time or 8 hrs to the Pacific Standard Time listed. Table 1 ------- Date Time N Lat. W Long. Mag ------------------------------------------------------------- 3/23 12:30 am 32 28.0 115 26.5 2.7 14 mi. SSE of Calexico 3/23 6:02 am 33 42.2 116 44.3 2.0 3 mi. SSW of Idyllwild 3/23 9:25 am 33 58.9 116 22.1 2.1 7 mi. E of Desert Hot Springs 3/23 5:53 pm 34 14.3 116 50.2 2.2 2 mi. SSE of Big Bear City 3/23 10:42 pm 32 45.2 115 26.6 2.2 6 mi. NE of Calexico 3/23 10:43 pm 32 44.5 115 26.1 2.4 " 3/23 10:44 pm 32 44.9 115 26.1 2.2 " 3/23 10:45 pm 32 44.3 115 26.0 2.3 " 3/24 4:17 am 34 24.6 116 28.4 2.2 20 mi. N of Yucca Valley 3/24 4:28 am 34 13.7 118 36.2 2.1 1 mi. N of Canoga Park 3/24 5:15 am 33 59.9 119 11.9 2.3 10 mi. S of Port Hueneme 3/24 2:23 pm 34 7.7 116 23.1 2.1 3 mi. E of Yucca Valley 3/24 3:00 pm 34 21.3 118 46.8 2.1 6 mi. NW of Simi Valley 3/24 6:10 pm 34 17.8 118 26.9 2.1 1 mi. NNW of San Fernando 3/24 6:58 pm 34 18.4 116 26.8 2.7 13 mi. N of Yucca Valley 3/24 7:30 pm 32 27.7 115 26.3 2.1 14 mi. SSE of Calexico 3/24 8:08 pm 34 18.0 118 27.3 3.0 1 mi. NW of San Fernando FELT 3/24 8:24 pm 34 17.8 118 27.0 2.5 " 3/24 9:47 pm 35 1.8 118 8.0 2.1 2 mi. SE of Mojave 3/24 10:33 pm 34 17.7 118 26.7 2.4 Under San Fernando 3/25 12:00 am 33 54.1 118 18.4 2.0 Gardena area 3/25 7:49 am 34 47.2 116 17.8 2.0 35 mi. SSW of Baker 3/25 1:40 pm 34 16.2 118 27.3 2.6 1 mi. SW of San Fernando FELT 3/25 3:37 pm 33 18.8 116 18.5 2.4 5 mi. NE of Borrego Springs 3/25 5:54 pm 34 18.1 118 26.5 2.4 1 mi. N of San Fernando 3/25 10:46 pm 32 29.1 115 28.3 2.0 12 mi. S of Calexico 3/26 5:17 am 32 31.7 116 10.6 2.0 17 mi. SW of Ocotillo 3/26 6:41 am 32 29.6 115 27.5 2.0 12 mi. S of Calexico 3/26 8:49 am 34 9.2 116 25.6 2.0 2 mi. NNE of Yucca Valley 3/26 12:49 pm 35 2.1 119 1.0 3.0 3 mi. WNW of the I5/99 interchange 3/26 12:49 pm 34 58.7 119 0.0 2.5 " 3/26 1:18 pm 35 0.1 119 0.8 2.3 " 3/26 2:01 pm 34 19.1 116 45.6 2.8 6 mi. NE of Big Bear City FELT 3/26 4:23 pm 35 50.8 117 37.7 2.0 15 mi. N of Ridgecrest 3/26 11:11 pm 34 37.6 116 38.7 3.0 21 mi. NE of Lucerne Valley 3/27 7:34 am 33 21.3 116 25.9 2.2 7 mi. NNW of Borrego Springs 3/27 8:26 am 33 59.3 116 26.5 3.3 3 mi. ENE of Desert Hot Springs; FELT 3/27 8:42 am 34 21.3 118 41.9 2.0 5 mi. N of Simi Valley 3/27 12:15 pm 32 23.9 115 28.1 2.4 18 mi. S of Calexico 3/27 1:17 pm 34 18.9 116 45.3 2.1 6 mi. ENE of Big Bear City 3/27 2:13 pm 34 27.5 116 31.3 2.5 23 mi. N of Yucca Valley 3/27 3:26 pm 34 1.2 118 59.4 2.1 3 mi. WSW of Leo Carrillo State Beach 3/27 5:26 pm 33 21.3 116 25.8 2.2 7 mi. NNW of Borrego Springs 3/27 9:36 pm 35 19.1 119 24.8 2.9 12 mi. N of Taft 3/27 10:38 pm 33 35.3 116 37.4 2.2 3 mi. NE of Anza 3/27 11:07 pm 33 20.9 116 25.6 2.3 7 mi. NNW of Borrego Springs 3/28 8:37 am 32 26.0 115 28.1 2.1 16 mi. S of Calexico 3/28 10:44 am 33 7.7 116 0.9 2.6 6 mi. E of Ocotillo Wells 3/28 11:13 am 32 29.4 115 28.4 3.2 12 mi. S of Calexico 3/28 6:03 pm 34 14.2 118 29.1 2.0 2 mi. E of Northridge 3/28 9:36 pm 33 25.9 119 0.2 2.0 4 mi. SE of Santa Barbara Is. 3/28 9:50 pm 33 20.7 116 15.3 2.0 9 mi. NE of Borrego Springs 3/29 12:32 am 35 21.1 117 32.9 2.4 19 mi. SSE of Ridgecrest 3/29 4:07 pm 33 43.8 118 39.9 2.0 14 mi. WSW of Palos Verdes Point 3/29 5:36 pm 32 28.4 115 27.0 2.1 13 mi. S of Calexico -------------------------------------------------------------