SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey August 17, 1995 Weekly Earthquake Report for Southern California ------------------------------------------------ August 10 - 16, 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, August 10, Pacific Daylight Time, to midnight Wednesday night, August 16, 1995, Pacific Daylight Time. We recorded 328 earthquakes of during the 7-day period covered. The activity this week was higher than it has been in the past few weeks, although still within the range expected for "statistical fluctuations". The largest quake was a M3.4 Landers aftershock, in the Yucca Valley area, on Tuesday morning. It was felt in the Yucca Valley. The focal mechanism shows "normal", or extentional, along with strike-slip, which is slightly unusual for that part of the Landers aftershock zone. Other M3+ quakes include a M3.2 in the Banning area in the wee hours of Saturday morning. There was also a M3.2 on Monday evening in the Coso Range area, east of Owens Valley. This quake also showed a "normal" or extensional mechanism, which is normal for that area, near the eastern edge of the Basis and Range Province, an large extensional region that covers most of Nevada and Utah as well as Owens Valley. Also on Monday evening, there was a M3.0 near Hemet, which was felt. Its focal mechanism was mostly strike-slip, consistant with the San Jacinto Fault zone. In addition, there were a couple of M2.9's: the first on Wednesday morning, in the Wheeler Ridge area near the I5 Grapevine Grade, and the second a Landers aftershock north of Yucca Valley late Wednesday night. The latter was felt. There was a report of two quakes being felt but no time separation was given, so it is not clear if the P and S waves of the M2.9 were both felt separately, or if some very sensitive individual picked up the M2.1 foreshock one minute earlier. 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 ------------------------------------------------------------- 8/10 3:51 am 34 37.1 116 35.2 2.0 23 mi. ENE of Lucerne Valley 8/10 2:02 pm 34 59.7 119 3.5 2.0 6 mi. W of Wheeler Ridge 8/10 2:03 pm 36 24.6 120 54.4 2.7 35 mi. WNW of Coalinga 8/11 5:31 am 35 1.9 117 0.1 2.4 9 mi. N of Barstow 8/11 5:46 am 34 37.9 120 23.4 2.0 3 mi. E of Lompoc 8/11 10:38 am 34 36.5 116 37.9 2.0 21 mi. ENE of Lucerne Valley 8/11 10:46 am 34 57.9 116 56.2 2.6 7 mi. NE of Barstow 8/12 12:53 am 33 53.3 117 44.0 2.5 4 mi. E of Yorba Linda 8/12 2:57 am 33 59.1 116 54.2 3.2 4 mi. NNW of Banning 8/12 3:48 am 34 55.3 116 55.6 2.0 5 mi. ENE of Barstow 8/12 7:11 am 35 55.2 117 40.7 2.8 20 mi. N of Ridgecrest 8/12 9:48 am 32 57.5 117 52.9 2.5 28 mi. ENE of San Clemente Is. (SE tip) 8/12 7:41 pm 34 1.8 116 23.7 2.0 6 mi. SSE of Yucca Valley 8/13 1:19 am 34 21.7 118 39.6 2.3 6 mi. NNE of Simi Valley 8/13 1:20 am 34 21.6 118 39.4 2.0 " 8/13 2:12 am 33 4.2 117 50.1 2.1 27 mi. SSW of Dana Point 8/13 4:33 am 34 16.9 116 46.3 2.1 4 mi. ENE of Big Bear City 8/13 12:16 pm 34 5.3 116 22.6 2.0 4 mi. ESE of Yucca Valley 8/13 4:49 pm 34 15.6 118 26.5 2.0 1 mi. S of Pacoima 8/13 5:10 pm 35 5.4 118 19.1 2.2 7 mi. ESE of Tehachapi 8/14 5:16 am 33 58.5 116 58.4 2.0 3 mi. N of Beaumont 8/14 2:02 pm 36 5.8 117 52.3 2.6 4 mi. SE of Haiwee Reservoir (S end) 8/14 4:22 pm 36 5.7 117 52.4 2.0 " 8/14 5:00 pm 36 5.7 117 52.5 2.1 " 8/14 5:29 pm 33 54.0 118 12.4 2.0 1 mi. NE of Compton 8/14 9:12 pm 35 47.1 118 2.0 3.2 18 mi. SSW of Coso Junction 8/14 9:29 pm 35 47.2 118 2.2 2.0 " 8/14 9:32 pm 35 47.2 118 2.1 2.3 " 8/14 10:17 pm 33 46.9 116 55.3 3.0 3 mi. NE of Hemet FELT 8/14 10:28 pm 35 47.3 118 2.0 2.0 18 mi. SSW of Coso Junction 8/15 3:29 am 35 47.2 118 2.0 2.3 " 8/15 9:03 am 34 10.2 116 27.5 3.4 3 mi. NNW of Yucca Valley FELT 8/15 11:37 am 34 33.7 116 25.2 2.4 29 mi. NNW of Joshua Tree 8/15 1:50 pm 35 1.9 116 58.9 2.0 10 mi. NNE of Barstow 8/16 2:38 am 34 25.6 118 35.8 2.2 2 mi. NW of Valencia 8/16 5:08 am 34 25.7 118 35.6 2.1 " 8/16 5:54 am 34 25.4 118 36.0 2.4 " 8/16 6:30 am 34 42.8 116 7.2 2.0 38 mi. S of Baker 8/16 7:15 am 34 56.7 118 59.5 2.9 3 mi. W of Grapevine 8/16 8:38 am 36 27.4 120 4.0 2.2 24 mi. SW of Fresno 8/16 12:10 pm 35 5.7 118 43.5 2.0 9 mi. SE of Arvin 8/16 11:44 pm 34 15.7 116 26.1 2.1 9 mi. N of Yucca Valley 8/16 11:45 pm 34 15.5 116 26.1 2.9 " FELT 8/16 11:50 pm 34 15.8 116 26.1 2.1 " -------------------------------------------------------------