Northern California Seismicity Report for the week ending Dec 21, 2000

This report provides a brief summary of earthquake activity recorded by the U.S. Geological Survey Northern California Seismic Network in Menlo Park and the University of California Berkeley Seismological Laboratory. It is automatically generated each Wednesday shortly after midnight, Universal time (UT). UT (ie., Greenwich Mean Time) is 8 hours ahead of PST or 7 hours ahead of PDT.

Because it is not possible to review all of the earthquakes before this report is generated, it may contain errors. Please report errors or provide suggestions and comments to ncsn@andreas.wr.usgs.gov

The report no longer includes maps showing earthquakes for the entire US or world. Those maps are now available from the U.S.G.S. National Earthquake Information Center. In addition, all earthquake data can be retrieved from the Northern California Earthquake Data Center.

Please note that some of the earthquake data in this report have been reviewed by seismic analysts. Consequently, the parameters that describe the hypocenter, magnitude, origin time, and solution statistics may differ slightly from the information contained on the real-time earthquake web page. The differences reflect revised arrival times at seismic stations and the analysts' decisions to include or exclude information from seismic stations.

The minimum magnitude ( M) values in the following bullets reflect the smallest earthquake which the network can routinely record within the region. During the previous seven-day period ending at midnight (UT) Wednesday, our seismic networks recorded

• 27 M >2.0 earthquakes in Northern and Central California (map) (within dashed polygon of figure).

The largest event to occur this week in this region was a light earthquake of magnitude 4.6, 8 miles NNW of Burney, CA at 11:39 PM UTC Wednesday, 12 20, 2000 (03:39 PM PST Wednesday, Dec 20, 2000).

This sequence began on 12/15 21:07 PST with a M3.1 earthquake. A few small aftershocks followed over the next 4 days, but on 12/20 at 14:55 PDT activity resumed with a M3.8 earthquake. As of the time of this report, there were a total of 30 earthquakes recorded, the largest being the M4.6 described above. There were 8 earthquakes above M3.0. This sequence occurred in the same location of a M3.7 earthquake on 7/22/1987 and two quakes of M3.5 and 3.6 on 03/27/1998. The earthquakes were felt throughout the Hat Creek - Burney region. There are numerous mapped faults in the region, but it is unknown at this time whether these quakes can be associated with one of these faults.

• 14 M >1.2 earthquakes in the San Francisco Bay area (map).

The largest event to occur this week in this region was a minor earthquake of magnitude 3.3, 10 miles E of San Jose City Hall, CA at 06:58 PM UTC Thursday, 12 14, 2000 (10:58 AM PST Thursday, Dec 14, 2000).

This earthquake occurred on the Calaveras fault just north of the hypocenter of the M6.2 Morgan Hill earthquake. This section of the Calaveras has been the site of more than 100 M3+ quakes since 1968. The 12/14 quake was widely felt throughout the south San Francisco Bay region, and as far away as Livermore Valley, Pacifica, and Santa Cruz.

• 15 M >1.2 earthquakes in the Long Valley region (map).

The largest event to occur this week in this region was a microearthquake of magnitude 2.2, 6 miles WSW of Toms Place, CA at 03:06 AM UTC Sunday, 12 17, 2000 (07:06 PM PST Saturday, Dec 16, 2000).

The following table provides a listing of all M >2 earthquakes that occurred this week. An explanation of the entries in the table is available.

---ORIGIN TIME (UT)--- -LAT N-- --LON W-- DEPTH  N RMS ERH ERZ LOC    PREF AZ MIN S. PAGE   1
YEAR MON DA HRMN  SEC  DEG MIN  DEG  MIN    KM  RD SEC  KM  KM REMKS  MAG  GAP DS PF

2000 DEC 14 1310 43.55 37 21.22 121 43.21  6.10 57 .04  .1  .2 ALU    2.0D  53  3 NN
2000 DEC 14 1858 21.73 37 20.97 121 42.86  8.17 78 .05  .1  .3 ALU    3.3D  51  4 NN
2000 DEC 14 1917 25.17 37 20.87 121 42.76  7.97 74 .05  .1  .2 ALU    2.8D  52  4 NN
2000 DEC 14 1917 59.34 37 20.63 121 42.75  9.02  9 .03  .5 1.0 ALU    2.2D 134 10 WW
2000 DEC 15 0758 37.68 38 48.94 122 48.15  3.81 26 .05  .2  .3 GEY    2.1D  47  1 NN
 
2000 DEC 16 0226  1.22 37 17.17 119 23.35 34.14 34 .07  .4  .8 KAI    2.6D  83 21 NN
2000 DEC 16 0249 58.13 37 19.00 119 24.12 23.35 30 .41  .9 2.2 KAI  # 2.2D 172 21 NN
2000 DEC 16 0507 11.70 40 59.22 121 41.57 13.75 39 .21  .3 1.9 SHA    3.1D  80 27 NN
2000 DEC 16 0633 35.68 36 52.99 121 37.01  7.40 65 .09  .2  .3 SJB    2.7D  52  2 NN
2000 DEC 16 1400 15.06 40 19.33 124  7.48 30.02 20 .06  .4  .7 MEN    3.0D 117 11 NN
 
2000 DEC 17 0306 21.05 37 32.56 118 46.71  9.97 29 .06  .4  .7 MOR    2.2D 103  7 NN
2000 DEC 17 0745 18.45 40 59.18 121 41.29  2.61 15 .12  .410.7 SHA  - 2.3D  82 27 NN
2000 DEC 18 0240 20.37 36  4.65 119 59.16  9.07 54 .33  .4  .7 COA    2.4D  67 11 NN
2000 DEC 18 1516 44.42 40 59.05 121 40.73  4.97  8 .06  .5 8.6 SHA  - 2.0D  91 27 WW
2000 DEC 19 1458 40.93 36 14.69 120 48.12 10.16 32 .05  .2  .4 BIT    2.3D  81  3 WW
 
2000 DEC 20 2012  0.17 40 54.49 123 36.48 28.18 10 .05  .4  .9 EUR    2.5D  68 11 WW
2000 DEC 20 2255 51.89 40 59.13 121 41.22 13.01 42 .21  .3 1.5 SHA    3.8L  79 27 WW
2000 DEC 20 2259 38.62 40 59.30 121 41.31 14.15 52 .25  .4 1.5 SHA    3.8L  79 27 WW
2000 DEC 20 2301 39.45 41  2.10 121 47.15  5.36  9 .43 2.131.4 SHA -  2.2D 124 29 WW
2000 DEC 20 2306 23.58 40 59.24 121 41.36  5.00 10 .11  .5 9.9 SHA -  2.4D  82 27 WW
 
2000 DEC 20 2316  5.71 40 59.56 121 42.04  2.83  8 .17  .915.6 SHA -  2.4D 168 27 WW
2000 DEC 20 2322 54.52 40 59.39 121 41.91 11.16 53 .29  .4 1.7 SHA    4.3L 109 34 WW
2000 DEC 20 2325 57.36 40 58.94 121 40.91  4.99 12 .08  .3 8.1 SHA -  2.5D  83 27 WW
2000 DEC 20 2333 20.64 40 59.24 121 41.97 14.81 29 .21  .4 2.3 SHA    3.1L  79 27 WW
2000 DEC 20 2334 43.28 40 57.92 121 40.71 22.96  9 .08  .9 2.7 SHA    2.4D 223 43 WW
 
2000 DEC 20 2339 14.81 40 59.37 121 41.80 19.34 49 .24  .4 1.2 SHA    4.6L 109 34 WW
2000 DEC 20 2342  2.68 40 59.67 121 40.95 12.24 20 .21  .6 4.5 SHA    3.0L  83 26 WW