SOUTHERN CALIFORNIA
	     	           SEISMOGRAPHIC NETWORK

			  A Cooperative Project of
	          Caltech and the U.S. Geological Survey


						December 5, 1996

		Weekly Earthquake Report for Southern California
		------------------------------------------------
        	         November 27 - December 4, 1996                   

	Prepared by:  Kate Hutton, Seismological Laboratory
		      (kate@bombay.gps.caltech.edu)
		      Lucy Jones, Jim Mori, U. S. Geological Survey
		      California Institute of Technology

	For further information, please contact the authors or the 
	Caltech Public Relations Office at 818-395-6327.  For daily 
	updates, call our Earthquake Information Hotline: 818-395-6977.
			--------------------------------
	This week's Report covers the time period from midnight Thursday
	morning, November 27, Universal Time (ie. GMT), to midnight 
	Wednesday night, December 4, Universal Time.  In local time, 
	the period of coverage is from 4 p.m., November 26, Pacific 
	Daylight Time, to 4 p.m., December 4, Pacific Daylight Time.
	Due to the Thanksgiving holiday, last week's Report was one day
	early, making this week's longer than usual.  We detected and 
	processed 1,052 earthquakes during the six-day period covered.  
	Due to a combination of high seismicity and a four-day weekend,
	about 100 small events are not processed yet; so this total is
	a lower bound on the week's seismicity.
		The major events of the week were: a M4.1 Landers after-
	shock late last Wednesday afternoon, along with a few aftershocks
	up to M3.1, and a Mw5.3 in the Coso Range east of Coso Junction,
	with a large number of aftershocks, up to M3.7.
		The M4.1 was a typical Landers aftershock, with a mostly
	north northwest trending strike-slip mechanism.  It was located 
	very close to the epicenter of the Mw6.1 Joshua Tree quake that 
	preceded the Landers earthquake by two months.  This week's event 
	was felt fairly widely, in the Yucca Valley and Desert Hot 
	Springs area.
		The Coso earthquake occurred in the area of the Coso 
	geothermal fields, where there are frequent small quakes.  
	This region has had vigorous swarms in the past, consisting of 
	many small earthquakes with several M4's, in 1981, 1982-83, 1985
	and 1992.  The 1995-96 Ridgecrest sequence that included 3 M5+ 
	events occurred in an area 15 to 20 miles to the south.  Focal 
	mechanisms from both the first motions and the long-period 
	surface waves showed a strike-slip solution with northeast and 
	northwest nodal planes.  The distribution of relocated after-
	shocks seems to be elongated in a northwest-southeast direction, 
	suggesting right-lateral slip on a northwest trending fault 
	plane.  The Coso earthquake is producing a robust aftershock 
	sequence, as is typical of the Owens Valley region.  Given this 
	rate of activity, we would expect to see a few more aftershocks 
	above M3 in the next couple of weeks.
		In hindsight, we identified a small "foreshock" sequence 
	that occurred 27 hours before the mainshock and had 3 M2 earth-
	quakes with several smaller events (see last week's Report).  The 
	closest telemetered strong-motion instrument recorded 2% g at 
	Ridgecrest, about 25 miles to the south. 
                Table 1 lists the quakes this week that were M2.0 or
        larger in the central part of the coverage area.  To make the
	list managably short, Coso quakes are listed only if they are
	M2.5 or larger.  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  
	-------------------------------------------------------------
        11/26  5:42 pm  33 57.2  116 18.8  4.1  12 mi. S of Joshua Tree
						FELT
        11/26  5:44 pm  33 57.5  116 18.5  3.0  	"
        11/26  5:51 pm  33 57.9  116 18.9  2.0  	"
        11/26  6:16 pm  33 57.2  116 18.8  3.1  	"
        11/26  6:24 pm  33 57.4  116 18.8  2.3  	"
        11/26  9:06 pm  33 57.5  116 18.7  2.2  	"
        11/27 12:11 am  33 45.9  118 27.1  2.1  1 mi. WSW of Palos Verdes 
						Point
        11/27 12:18 am  33 57.4  116 18.8  2.4  12 mi. S of Joshua Tree
        11/27 12:22 am  33 57.3  116 18.7  2.0  	"
        11/27 12:50 am  33 57.3  116 18.9  2.2  	"
        11/27  1:19 am  33 12.6  116  2.0  2.2  6 mi. SW of Salton City
        11/27  9:45 am  34 12.1  117 24.6  2.2  1 mi. SSW of Devore
        11/27 10:01 am  34 14.8  119 40.4  2.5  12 mi. S of downtown Santa 
						Barbara
        11/27 12:07 pm  36  1.4  117 51.5  2.0  5 mi. ESE of Coso Junction
        11/27 12:17 pm  36  4.5  117 39.0  5.3  Coso Range, 16 mi. E of 
						Coso Junction
						WIDELY FELT
        11/27 12:20 pm  36  3.2  117 39.3  2.5  	"
        11/27 12:24 pm  36  4.7  117 38.9  2.5  	"
        11/27 12:25 pm  36  5.5  117 39.0  2.8  	"
        11/27 12:39 pm  36  5.1  117 39.2  2.5  	"
        11/27 12:46 pm  36  4.2  117 39.9  2.6  	"
        11/27 12:46 pm  36  5.2  117 38.8  2.9  	"
        11/27  2:29 pm  36  4.5  117 38.1  3.7  	"
        11/27  2:30 pm  36  3.8  117 38.0  2.9  	"
        11/27  2:31 pm  36  5.0  117 38.8  2.5  	"
        11/27  2:48 pm  36  4.3  117 39.3  2.6  	"
        11/27  3:41 pm  32 29.9  115 17.0  3.1  17 mi. SE of Calexico
        11/27  3:45 pm  32 29.6  115 16.8  2.2   	"
        11/27  3:48 pm  32 29.0  115 16.8  2.4   	"
        11/27  3:55 pm  36  5.0  117 39.3  2.5  16 mi. E of Coso Junction
        11/27  4:27 pm  36  3.8  117 40.3  2.5   	"
        11/27  4:40 pm  36  5.3  117 39.2  2.9   	"
        11/27  4:45 pm  36  4.6  117 39.3  2.7   	"
        11/27  4:45 pm  36  5.2  117 38.5  2.5   	"
        11/27  4:53 pm  36  3.9  117 38.4  2.5   	"
        11/27  4:56 pm  36  5.3  117 39.2  2.7   	"
        11/27  5:00 pm  33 59.8  116 17.9  2.2  9 mi. S of Joshua Tree
        11/27  5:01 pm  36  4.6  117 39.1  2.7  16 mi. E of Coso Junction
        11/27  5:18 pm  36  4.1  117 38.5  2.5   	"
        11/27  5:47 pm  34 56.3  116 39.9  2.0  20 mi. E of Barstow
        11/27  8:52 pm  36  5.1  117 39.0  2.6  16 mi. E of Coso Junction
        11/27  8:59 pm  36  5.0  117 39.0  2.6   	"
        11/27 11:41 pm  36  3.9  117 38.3  2.6   	"
        11/28 12:49 am  36  4.8  117 38.4  3.5   	"
        11/28 12:50 am  36  4.0  117 39.0  2.8   	"
        11/28  3:29 am  36  5.4  117 39.4  3.2   	"
        11/28  3:44 am  36  6.0  117 38.7  2.5   	"
        11/28  6:46 am  36  3.8  117 38.5  2.7   	"
        11/28  6:48 am  35 48.2  117 37.9  2.0  12 mi. N of Ridgecrest
        11/28  8:37 am  33 44.0  118  2.7  2.1  3 mi. N of Bolsa Chica 
						Beach             
        11/28 12:21 pm  36  5.3  117 39.5  2.5  16 mi. E of Coso Junction
        11/28  1:06 pm  36  5.5  117 39.0  2.5  	"
        11/28  1:47 pm  36  5.2  117 39.1  3.5  	"
        11/28  1:49 pm  36  5.4  117 39.1  2.5  	"
        11/28  2:03 pm  36 34.7  117 53.5  2.4  9 mi. E of Lone Pine
        11/28  2:05 pm  36  5.4  117 39.1  3.7  16 mi. E of Coso Junction
        11/28  2:51 pm  36  4.7  117 39.9  2.6  	"
        11/28  3:10 pm  36  5.3  117 39.5  2.6  	"
        11/28  3:39 pm  36 34.5  117 53.1  2.7  10 mi. E of Lone Pine
        11/28  3:45 pm  36  5.0  117 38.8  2.8  16 mi. E of Coso Junction
        11/28  7:15 pm  36  3.8  117 39.0  2.8  	"
        11/29 12:57 am  36  7.1  117 37.7  2.5  	"
        11/29  4:21 am  36  4.2  117 38.4  2.5  	"
        11/29  5:42 am  36  4.5  117 38.0  2.7  	"
        11/29 10:01 am  36  5.1  117 38.5  2.5  	"
        11/29 10:14 am  34 17.7  116 11.8  2.2  12 mi. NNE of Joshua Tree
        11/29 10:34 am  36  5.0  117 39.2  2.6  16 mi. E of Coso Junction
        11/29  1:31 pm  36  5.4  117 39.3  3.1  	"
        11/29  3:44 pm  32 45.9  115 26.8  2.2  6 mi. ESE of El Centro
        11/29  7:46 pm  36  5.4  117 38.3  2.6  16 mi. E of Coso Junction
        11/30  8:28 am  36  5.4  117 39.3  2.7  	"
        11/30  9:54 am  33 21.2  116 17.9  2.1  8 mi. NNE of Borrego 
						Springs
        11/30 10:46 am  36  5.2  117 38.9  2.5  16 mi. E of Coso Junction
        11/30 11:03 am  36  4.0  117 38.8  2.8  	"
        11/30 12:15 pm  36  5.6  117 39.3  2.8  	"
        11/30  2:11 pm  36  5.6  117 39.1  3.6  	"
        12/1  11:42 pm  33 57.5  116 19.4  2.1  10 mi. E of Desert Hot 
						Springs
        12/1   7:29 am  34 35.7  116 37.0  2.3  21 mi. ENE of Lucerne 
						Valley
        12/1   7:30 am  34 35.4  116 37.1  3.1  	"
        12/1  10:45 am  36  5.4  117 39.4  2.8  16 mi. E of Coso Junction
        12/1  12:25 pm  34 34.4  116 32.8  2.2  24 mi. ENE of Lucerne 
						Valley
        12/1   2:04 pm  36  3.9  117 38.4  2.6  16 mi. E of Coso Junction
        12/1   6:13 pm  36  4.6  117 38.2  2.5  	"
        12/1   7:47 pm  33 38.5  116 43.3  2.4  6 mi. NNW of Anza
        12/1  11:18 pm  36  5.7  117 39.2  2.5  16 mi. E of Coso Junction
        12/2   5:55 am  34 20.4  116 27.9  2.0  15 mi. N of Yucca Valley
        12/2   6:02 am  34 20.5  116 28.0  2.1  	"
        12/2  10:52 am  34 19.4  118 32.3  2.2  3 mi. S of Newhall
        12/2  10:59 am  34  7.0  116 59.6  2.1  6 mi. NNE of Yucaipa
        12/2   2:15 pm  33 14.2  116 46.5  2.5  Under Lake Henshaw
        12/2   8:28 pm  36  5.1  117 38.1  2.9  16 mi. E of Coso Junction
        12/2   8:28 pm  36  4.9  117 38.2  2.8  	"
        12/2  10:34 pm  36  5.6  117 39.4  2.8  	"
        12/3   5:36 am  34 16.4  118 30.9  2.0  Under Granada Hills
        12/3  10:00 am  36  5.5  117 39.3  2.9  16 mi. E of Coso Junction
        12/3  10:36 am  36  5.7  117 39.1  2.7  	"
        12/3  12:44 pm  36  3.8  117 39.1  3.3  	"
        12/4   1:18 am  34 27.0  116 30.8  2.5  23 mi. N of Yucca Valley
        12/4   4:38 am  35 43.3  117 37.2  2.2  7 mi. NNE of Ridgecrest
        12/4   4:55 am  36  4.2  117 39.1  2.6  16 mi. E of Coso Junction
        12/4   3:15 pm  34 28.5  119 21.8  2.2  6 mi. WNW of Ojai
	-------------------------------------------------------------