March 10, 1994 Weekly Earthquake Report for Southern California ------------------------------------------------ March 3 - 9, 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, March 3, Pacific Standard Time, to midnight Wednesday night, March 9, Pacific Standard Time. There are 584 this week. It was not a particularly exciting week, as recent weeks have gone. Seven events were felt by the public, six of them Northridge aftershocks. The seventh one was in the Watts/Lynnwood area, M2.9 last Thursday morning. The week's largest quake was a Landers aftershock, in a remote area: M3.7 very early Monday morning. At present, as we continue to process Northridge aftershock data, we have the following cumulative statistics for the sequence: M3.0 through 3.9: 310 M4.0 through 4.9: 43 M5.0 through 5.9: 6 The fluctuation in the numbers from tabulation to tabulation is due to revision of some of the magnitudes. For example, some quake previously labeled as M2.9's became M3.0's and vice versa. The total number of processed aftershocks exceeds 5,500, and we are still working. The Northridge sequence continues to decay as expected. By adjusting the parameters of an equation describing aftershock rates to fit the earlier part of the sequence, we can estimate, statistically speaking, future aftershocks. From this we would have expected about five M3.0 or larger this week, and we got, in fact, five. Next week we expect about four M3.0 or larger Northridge aftershocks. Recall that, three weeks ago, the expected number of M3.0 per week was eight. Recall also that, like the number of heads and tails in a series of coin tosses, these estimates are statistical. If our model is correct, they will agree with Nature on the average, but we cannot be expected to hit the exact numbers every 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 ------------------------------------------------------------- 3/3 12:41 am 34 20.5 118 27.6 2.5 4 mi. NNW of San Fernando 3/3 1:53 am 34 22.8 118 29.5 3.2 1 mi. E of Newhall; FELT 3/3 8:24 am 34 57.3 116 47.6 2.0 13 mi. ENE of Barstow 3/3 9:24 am 32 20.2 115 15.4 2.5 26 mi. SSE of Calexico 3/3 9:27 am 32 16.1 115 14.9 3.5 31 mi. SSE of Calexico 3/3 9:34 am 33 55.8 118 12.4 2.9 2 mi. WSW of the Watts Tower FELT 3/3 7:58 pm 34 18.6 118 28.3 2.5 2 mi. NW of San Fernando 3/4 12:28 am 34 0.2 116 19.3 2.3 10 mi. SE of Yucca Valley 3/4 6:25 am 34 20.6 116 27.9 2.1 15 mi. N of Yucca Valley 3/4 8:24 am 34 58.6 116 56.6 2.9 7 mi. NE of Barstow 3/4 10:10 am 35 40.7 117 36.7 2.0 4 mi. NE of Ridgecrest 3/4 11:40 am 35 48.2 118 24.9 2.3 11 mi. NNE of the town of Lake Isabella 3/4 1:19 pm 33 52.8 117 41.0 2.4 6 mi. W of Corona 3/4 2:01 pm 34 23.4 118 37.6 3.1 3 mi. SW of Magic Mtn. 3/4 3:48 pm 34 11.9 118 33.9 2.6 2 mi. E of Canoga Park; FELT 3/4 5:23 pm 34 57.9 116 56.7 2.2 6 mi. NE of Barstow 3/4 10:20 pm 35 1.3 116 58.1 2.3 9 mi. NNE of Barstow 3/5 3:57 am 33 11.8 115 57.8 2.4 5 mi. S of Salton City 3/5 4:55 am 34 23.3 116 28.1 2.2 18 mi. N of Yucca Valley 3/5 6:23 am 34 18.6 118 28.5 3.1 2 mi. NW of San Fernando FELT 3/5 3:37 pm 34 18.4 118 28.7 3.1 " FELT 3/5 9:24 pm 34 16.5 118 27.5 2.6 1 mi. WSW of San Fernando 3/6 1:56 am 34 37.3 116 33.3 2.3 25 mi. ENE of Lucerne Valley 3/6 2:23 am 34 14.9 118 28.5 2.9 3 mi. SW of San Fernando FELT 3/6 2:41 am 34 17.8 118 27.6 2.6 1 mi. NW of San Fernando 3/6 2:44 am 34 29.2 116 27.6 2.1 25 mi. N of Yucca Valley 3/6 8:20 am 34 59.0 116 56.8 2.3 7 mi. NNE of Barstow 3/6 10:19 am 34 21.2 118 31.3 2.9 1 mi. S of Newhall 3/6 2:53 pm 33 11.8 115 34.1 3.0 Obsidian Butte, 4 mi. SW of Niland 3/6 3:03 pm 33 11.5 115 33.7 2.3 " 3/6 6:15 pm 33 58.0 116 22.0 2.2 7 mi. E of Desert Hot Springs 3/7 1:11 am 34 37.4 116 36.3 3.7 22 mi. ENE of Lucerne Valley 3/7 1:26 am 34 37.5 116 36.0 2.0 " 3/7 2:17 am 34 37.1 116 36.7 2.3 " 3/7 3:44 am 34 37.4 116 36.1 2.2 " 3/7 7:15 am 34 37.3 116 36.6 2.1 " 3/7 3:16 pm 33 56.3 118 23.6 2.1 2 mi. ESE of LAX 3/7 4:07 pm 34 31.3 116 32.0 2.1 25 mi. NE of Big Bear City 3/7 6:24 pm 34 56.1 116 52.7 2.1 8 mi. ENE of Barstow 3/7 10:46 pm 34 58.4 116 57.4 2.1 7 mi. NNE of Barstow 3/8 4:53 am 34 14.7 118 27.5 3.4 2 mi. SSW of San Fernando FELT 3/8 7:44 am 34 41.4 116 10.1 2.1 38 mi. N of Twentynine Palms 3/8 9:19 am 34 1.9 117 8.4 2.0 2 mi. SE of Redlands 3/8 2:41 pm 34 27.6 116 29.3 2.1 23 mi. N of Yucca Valley 3/8 3:33 pm 33 58.0 118 24.8 2.0 1 mi. NE of LAX 3/8 6:51 pm 34 0.8 119 10.8 2.4 9 mi. S of Port Hueneme 3/8 8:30 pm 34 56.6 116 39.6 2.9 20 mi. E of Barstow 3/9 1:17 am 34 22.9 118 37.3 2.8 3 mi. SSW of Magic Mtn. 3/9 2:40 am 34 59.2 119 5.2 2.3 7 mi. WSW of the I5/99 interchange 3/9 5:53 am 34 15.2 118 29.2 2.6 2 mi. ENE of Northridge 3/9 6:49 am 33 58.9 118 32.3 2.1 3 mi. SW of Santa Monica 3/9 6:55 am 35 7.9 119 9.2 2.0 13 mi. NW of the I5/99 interchange 3/9 11:39 am 33 40.0 116 45.8 2.2 6 mi. SSW of Idyllwild 3/9 1:12 pm 34 2.9 117 15.3 2.3 2 mi. ESE of the I10/I215 interchange, Loma Linda 3/9 9:12 pm 34 15.3 118 27.9 2.5 2 mi. SW of San Fernando 3/9 9:26 pm 34 3.8 118 51.1 2.5 5 mi. NNW of Pt. Dume 3/9 11:59 pm 34 16.8 118 27.7 2.7 1 mi. W 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.