June 2, 1994 Weekly Earthquake Report for Southern California ------------------------------------------------ May 26 - June 1, 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, May 26, Pacific Daylight Time, to midnight Wednesday night, June 12, Pacific Daylight Time. We recorded 394 earthquakes this week. Several Northridge aftershocks were felt this week. On Saturday, a M3.2 at 7:48 am, another M3.2 at 10:14 am, and a M3.7 at 10:15 am all occurred in the Simi Valley area, at the western end of the Northridge aftershock zone. Last night, Wednesday night, there was a M3.7 near San Fernando, at the eastern end of the zone, that was felt. These two M3.7's were the week's largest quakes. Both had focal mechanisms that were mostly thrust, like most Northridge aftershocks. Four events above M3 is above the weekly average of two such events, but it makes up for the several previous weeks that only had one. One non-aftershock was also felt: a M3.3 in San Bernardino last Thursday afternoon, very close to the San Jacinto fault. This event was very deep, at 18 km. One of the two fault planes indicated by the focal mechanism is almost horizontal. This type of focal mechanism has been observed several times at great depths in the San Bernardino Mountains. Three more M3 plus quakes went unfelt by the public. One, a M3.3, was on Friday evening, near Palomar Observatory in San Diego County (barely). On Sunday evening, there was a M3.5 in the Coso geothermal area, along Rt. 395 on the way to Mammoth Lakes. Then on Monday evening, there was another M3.3 in the Ocotillo Wells area, east of Borrego Springs, probably associated with a branch of the San Jacinto fault. If people felt these small events, they did not bother calling. The table lists the quakes 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 Daylight Time listed. Table 1 ------- Date Time N Lat. W Long. Mag ------------------------------------------------------------- 5/26 12:49 am 34 36.3 116 37.7 2.0 21 mi. ENE of Lucerne Valley 5/26 12:49 am 34 17.5 118 27.4 2.6 1 mi. NW of San Fernando 5/26 8:31 am 34 18.3 118 24.4 2.1 2 mi. NE of San Fernando 5/26 3:26 pm 34 6.6 117 19.4 3.3 1 mi. W of downtown San Bernardino; FELT 5/26 3:45 pm 34 20.7 118 35.1 2.6 4 mi. SW of Newhall 5/26 3:45 pm 34 17.0 118 38.5 2.4 3 mi. E of Simi Valley 5/26 5:46 pm 32 58.5 117 47.0 2.2 27 mi. WSW of Oceanside 5/26 6:15 pm 34 16.6 118 28.8 2.0 2 mi. W of San Fernando 5/26 6:42 pm 34 21.6 118 30.8 2.2 1 mi. SSE of Newhall 5/27 1:18 am 33 18.5 116 17.6 2.0 5 mi. NE of Borrego Springs 5/27 3:05 am 34 18.5 120 36.3 2.5 13 mi. SW of Pt. Conception 5/27 10:17 am 34 13.5 116 45.2 2.5 6 mi. ESE of Big Bear City 5/27 7:46 pm 33 24.9 116 51.0 3.3 4 mi. N of Palomar Observatory 5/27 11:35 pm 34 23.5 116 27.4 2.1 18 mi. N of Yucca Valley 5/28 12:44 am 34 18.7 116 27.2 2.4 13 mi. N of Yucca Valley 5/28 3:18 am 33 54.6 118 21.1 2.0 2 mi. SSW of Hollywood Park Racetrack 5/28 7:48 am 34 21.3 118 41.2 3.2 5 mi. NNE of Simi Valley FELT 5/28 7:49 am 34 21.2 118 41.9 2.9 " 5/28 8:02 am 34 16.4 118 25.1 2.1 1 mi. ESE of San Fernando 5/28 8:19 am 34 21.2 118 40.9 2.7 5 mi. NNE of Simi Valley 5/28 9:37 am 35 38.7 117 38.4 2.0 2 mi. NE of Ridgecrest 5/28 10:14 am 34 21.3 118 41.0 3.2 5 mi. NNE of Simi Valley FELT 5/28 10:15 am 34 21.3 118 40.9 3.7 " FELT 5/28 11:09 am 34 37.0 116 37.0 2.0 22 mi. ENE of Lucerne Valley 5/28 11:30 am 34 37.4 116 33.0 2.5 25 mi. ENE of Lucerne Valley 5/28 1:19 pm 34 18.2 118 23.5 2.3 3 mi. ENE of San Fernando 5/28 2:27 pm 33 53.7 118 39.5 2.0 9 mi. S of Malibu 5/28 3:40 pm 34 22.3 118 32.7 2.4 1 mi. WSW of Newhall 5/28 8:19 pm 34 34.9 119 48.3 2.1 10 mi. N of Goleta 5/28 9:23 pm 34 15.7 116 26.9 2.0 9 mi. N of Yucca Valley 5/29 12:30 am 34 16.0 118 24.6 2.1 1 mi. ESE of San Fernando 5/29 12:52 pm 34 22.1 116 28.4 2.0 17 mi. N of Yucca Valley 5/29 2:45 pm 36 25.4 116 58.6 2.2 7 mi. WSW of Furnace Creek, Death Valley 5/29 4:26 pm 34 16.2 118 39.9 2.8 2 mi. ESE of Simi Valley 5/29 8:22 pm 36 4.4 117 51.7 3.5 5 mi. ENE of Coso Junction 5/29 11:27 pm 34 11.3 118 33.5 2.0 2 mi. ESE of Canoga Park 5/30 12:56 am 34 17.4 118 28.5 2.1 2 mi. WNW of San Fernando 5/30 1:52 am 32 15.9 115 15.2 2.7 31 mi. SSE of Calexico 5/30 1:56 am 36 38.4 118 21.2 2.1 5 mi. NW of Mt. Whitney 5/30 5:24 am 34 15.7 118 35.7 2.5 4 mi. N of Canoga Park 5/30 8:42 am 34 36.9 116 37.1 2.0 22 mi. ENE of Lucerne Valley 5/30 8:43 am 34 13.3 118 35.6 2.9 1 mi. NNE of Canoga Park 5/30 12:27 pm 34 19.5 118 25.0 2.3 3 mi. NNE of San Fernando 5/30 5:57 pm 34 16.0 118 27.8 2.0 1 mi. SW of San Fernando 5/30 6:53 pm 34 17.7 118 26.8 2.1 1 mi. NNW of San Fernando 5/30 8:03 pm 33 12.1 116 3.0 3.3 6 mi. NE of Ocotillo Wells 5/30 8:32 pm 34 15.9 118 28.7 2.0 2 mi. WSW of San Fernando 5/30 8:32 pm 34 30.4 116 31.0 2.0 27 mi. N of Yucca Valley 5/31 1:19 am 34 20.1 118 27.5 2.5 3 mi. NNW of San Fernando 5/31 4:10 am 34 16.8 118 26.7 2.2 Under San Fernando 5/31 5:33 pm 34 18.7 118 34.1 2.3 5 mi. SSW of Newhall 6/1 4:30 am 34 25.3 118 22.1 2.0 10 mi. NNE of San Fernando 6/1 2:37 pm 34 21.1 118 33.3 2.0 2 mi. SW of Newhall 6/1 8:27 pm 34 16.6 118 27.4 3.7 1 mi. WSW of San Fernando FELT 6/1 8:32 pm 34 16.4 118 27.5 2.5 " 6/1 11:59 pm 36 4.6 117 51.3 2.0 5 mi. ENE of Coso Junction ------------------------------------------------------------- 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.