SOUTHERN CALIFORNIA SEISMOGRAPHIC NETWORK A Cooperative Project of Caltech and the U.S. Geological Survey July 6, 1995 Weekly Earthquake Report for Southern California ------------------------------------------------ June 29 - July 5, 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, June 29, Pacific Daylight Time, to midnight Wednesday night, July 5, 1995, Pacific Daylight Time. We recorded 287 earthquakes of M1.0 or larger during the 7-day period covered. We were back to relative peace this week; there were no quakes above M3 in our region. In fact, the only quake that was reported as felt was a M2.4 (Landers aftershock) near Yucca Valley yesterday afternoon. The week's largest quake was a M2.9 in the Saline Valley area, northeast of Lone Pine. The L.A. Basin continued it's normal level of activity, which included three small events near the northern Newport- Inglewood fault zone, the largest of which was M2.1. The end of the quarter happened this week, however, so we have the statistical summary to present. Here are the totals for the past few years, listed by 3-month period. Two figures are listed for each quarter: the first is the total number of earthquakes, and the second is the total M3 or larger. 1st quarter 2nd quarter 3rd quarter 4th quarter all 3.0+ all 3.0+ all 3.0+ all 3.0+ 1990 3,483 56 2,627 45 2,225 27 2,403 31 1991 2,041 11 2,218 32 2,445 23 2,651 29 1992 3,618 40 10,288 744 25,500+ 801 10,700+ 166 1993 4,939 43 5,370 61 5,298 48 4,583 35 1994 10,915 417 5,967 43 5,400 48 5,031 40 1995 3,815 28 3,982 39 The totals for the Northridge sequence, from January 17, 1994 through the end of June 1995, are: All events 11,866 (446 more this quarter) 3.0 - 3.9 378 4.0 - 4.9 48 5.0 and up 10 That last M5 was, of course, the M5.0 that occurred on June 26, 1995. Similar totals for the Landers/Big Bear sequence are as follows: All events 56,000+ (1,735 more this quarter) 3.0 - 3.9 1,530 4.0 - 4.9 162 5.0 and up 21 The last M5 in the Landers/Big Bear sequence was a M5.0 that occurred on June 16, 1994. The + sign indicates that we are not finished with the data processing yet; however, all the events that are left to process are less than M3. Notice that this quarter's contribution from the Landers/Big Bear sequence is significantly larger than the contribution from the Northridge sequence. This is because of the larger magnitude of the Landers mainshock, Mw7.3 rather than Mw6.7. The aftershock sequence from the larger quake is expected to be much more prolific and last longer than that of the smaller one. 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 ------------------------------------------------------------- 6/29 12:14 am 35 2.1 117 0.2 2.3 10 mi. N of Barstow 6/29 1:27 am 34 7.1 116 52.0 2.2 2 mi. WNW of Mt. San Gorgonio 6/29 8:39 am 33 16.6 115 39.0 2.5 6 mi. SE of Bombay Beach 6/29 9:56 am 32 59.4 117 49.1 2.5 32 mi. SSW of San Clemente 6/29 10:43 am 33 58.5 117 2.8 2.2 5 mi. NW of Beaumont 6/29 2:13 pm 34 16.8 118 30.2 2.2 3 mi. NNE of Northridge 6/29 7:01 pm 34 21.3 116 54.1 2.5 6 mi. SSE of Lucerne Valley 6/29 10:53 pm 33 40.9 116 43.7 2.2 4 mi. S of Idyllwild 6/29 11:40 pm 34 17.2 118 40.8 2.0 1 mi. ENE of Simi Valley 6/30 4:26 am 34 1.4 118 22.5 2.1 1 mi. N of Baldwin Hills 6/30 1:07 pm 34 20.7 116 28.5 2.0 15 mi. N of Yucca Valley 6/30 1:07 pm 32 52.1 115 56.8 2.1 9 mi. NNE of Ocotillo 6/30 4:28 pm 35 1.4 116 57.7 2.0 10 mi. NNE of Barstow 6/30 6:30 pm 35 2.5 116 59.6 2.3 10 mi. N of Barstow 6/30 8:52 pm 36 0.5 117 48.7 2.3 Coso Range, 7 mi. ESE of Coso Junction 6/30 8:53 pm 36 0.5 117 48.9 2.2 " 6/30 8:54 pm 36 0.6 117 49.0 2.3 " 7/1 8:24 am 35 18.2 118 29.6 2.2 12 mi. NNW of Tehachapi 7/1 4:04 pm 33 57.6 118 19.2 2.1 1 mi. NE of Hollywood Park Racetrack 7/2 3:41 am 34 59.2 116 57.0 2.6 7 mi. NNE of Barstow 7/2 5:02 am 34 15.9 117 38.5 2.0 1 mi. SSE of Mt. Baldy 7/2 5:33 pm 34 12.8 116 26.5 2.1 6 mi. N of Yucca Valley 7/2 6:17 pm 33 20.9 116 26.0 2.4 7 mi. NNW of Borrego Springs 7/2 7:08 pm 35 4.1 116 39.3 2.2 23 mi. SSE of Goldstone (dry) Lake 7/2 8:02 pm 34 38.3 117 27.1 2.5 11 mi. NW of Victorville 7/2 10:16 pm 36 7.5 117 51.0 2.6 Coso Range, 5 mi. E of Haiwee Reservoir 7/2 10:21 pm 36 7.4 117 51.1 2.3 " 7/3 3:37 am 34 59.5 116 56.7 2.4 8 mi. NNE of Barstow 7/3 4:42 am 33 31.1 117 39.6 2.3 7 mi. NNW of San Clemente 7/3 11:02 am 32 52.6 117 43.2 2.2 29 mi. SW of Oceanside 7/3 12:58 pm 34 34.0 116 27.8 2.3 31 mi. N of Yucca Valley 7/3 1:53 pm 36 55.0 117 41.2 2.9 30 mi. NE of Lone Pine 7/3 4:11 pm 35 1.9 116 60.0 2.0 9 mi. N of Barstow 7/4 5:28 am 33 26.5 119 4.3 2.0 2 mi. SSW of Santa Barbara Is. 7/4 12:06 pm 33 12.9 116 4.6 2.5 5 mi. NNE of Ocotillo Wells 7/4 9:19 pm 34 13.1 117 2.8 2.1 3 mi. ENE of Running Springs 7/4 11:37 pm 35 0.9 116 57.5 2.6 9 mi. NNE of Barstow 7/5 3:37 am 34 7.0 116 24.4 2.4 2 mi. E of Yucca Valley FELT 7/5 5:20 am 34 13.6 118 29.6 2.4 2 mi. ESE of Northridge 7/5 6:13 am 33 56.1 116 37.7 2.0 7 mi. WSW of Desert Hot Springs 7/5 8:23 am 32 18.9 115 16.4 2.8 27 mi. SSE of Calexico 7/5 9:18 pm 33 31.7 117 38.7 2.5 7 mi. NNW of San Clemente -------------------------------------------------------------