Northern California Seismicity Report for the week ending Feb 08, 2001

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

• 32 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 an earthquake of magnitude 4.0, 7 miles NW of Alder Springs, CA at 11:03 PM UTC Friday, 02 02, 2001 (03:03 PM PST Friday, Feb 02, 2001).

Earthquakes of this size are not uncommon in this region. The largest in the last decade was a M4.2 quake that occurred in May of 1995. Since that time there have been a couple of other magnitude 3.0 or larger quakes on March 19, 1999, magnitude 3.3, and on November 16, 2000, magnitude 3.4. Those were in nearly the same location as this latest earthquake. And there have been many smaller quakes in the area in the last 10 years. Since this area is rather remote there were only a few felt reports for this earthquake.

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

The largest event to occur this week in this region was an earthquake of magnitude 3.5, 4 miles N of San Leandro, CA at 03:41 AM UTC Friday, 02 02, 2001 (07:41 PM PST Thursday, Feb 01, 2001).

This is the largest quake in this area for some time. The last one of similar size occurred on December 20, 1992 and was magnitude 3.5. This latest quake was reported felt over a large region, from Marin County in the north, to San Benito County in the south. Nearly 1900 people reported feeling it. This earthquake serves as a wake-up call to remind us that the Hayward fault is active and is the most likely fault to produce a magnitude 6.7 or larger earthquake in the next 30 years!

• 13 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 2.5, 8 miles SE of Mammoth Lakes, CA at 02:55 AM UTC Friday, 02 02, 2001 (06:55 PM PST Thursday, Feb 01, 2001).

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

2001 FEB  1 0619 38.95 40 24.98 124 24.55 28.20 22 .08  .8  .6 MEN    3.3D 223  9 NN
2001 FEB  1 0832 12.54 38 54.99 123  0.87  6.19 31 .07  .2  .5 MAA    2.0D  32 10 NN
2001 FEB  2 0120 24.85 37 46.94 122 10.19 11.25 65 .07  .1  .3 HAY    2.4D  28  8 NN
2001 FEB  2 0122 15.07 37 46.97 122 10.27 11.05 72 .06  .1  .3 HAY    2.5D  23  8 NW
2001 FEB  2 0255 16.06 37 33.47 118 52.53  6.34 35 .07  .2  .5 MOR    2.5D 105  5 NN
 
2001 FEB  2 0341 27.60 37 47.10 122 10.01 12.50 78 .09  .1  .3 HAY    3.5D  23  8 NN
2001 FEB  2 1119 40.86 37 19.88 118 31.91 14.16 34 .06  .5  .7 KAI    3.4D 145  4 NN
2001 FEB  2 1220 59.86 39 44.07 122 49.91  0.63 34 .11  .2 1.6 SAC  # 2.5D  73 13 NN
2001 FEB  2 1717 48.44 39 43.75 122 50.60  1.69 42 .27  .3 2.7 SAC  # 2.6D  41 14 NN
2001 FEB  2 1751 11.11 40 17.53 121 22.92  5.79 17 .04  .4  .9 ALM    3.0D 186 12 NN
 
2001 FEB  2 1810 48.93 40 17.63 121 23.25  6.03 10 .02  .8 1.7 ALM    2.0D 199 12 NN
2001 FEB  2 2001 26.94 40  2.25 121 36.35  7.64 23 .08  .4  .7 ALM    2.4D 119 14 NN
2001 FEB  2 2200 58.24 39 43.49 122 50.11  0.02 52 .20  .2  .6 SAC  # 3.5D  72 13 NN
2001 FEB  2 2303 11.45 39 43.79 122 48.50 11.79 76 .37  .3  .5 SAC    4.0D  19 12 NN
2001 FEB  2 2316 27.69 39 44.19 122 50.75  0.48 38 .23  .2 2.2 SAC    2.4D  85 14 NN
 
2001 FEB  3 0644 50.40 38 47.35 122 45.25  2.34 33 .04  .1  .4 GEY    2.3D  41  4 NN
2001 FEB  3 2033 38.36 37 58.35 122  2.12 14.73 71 .13  .2  .3 CON    2.9D  72  6 NN
2001 FEB  4 1552 25.09 38 48.41 122 48.69  1.18 10 .01  .2  .4 GEY    2.1D  56  1 WW
2001 FEB  4 2332 48.30 37 32.25 118 48.78  6.07 34 .07  .3  .6 MOR    2.2D 110  6 NN
2001 FEB  5 0314 28.94 38 49.58 122 48.29  4.63 34 .04  .1  .3 GEY    2.0D  37  2 NN
 
2001 FEB  7 0133 46.24 37  5.92 122 15.35 10.44 57 .14  .5  .6 ANN    2.7D 192  9 WW
2001 FEB  7 0447 54.54 39 32.70 123 22.16  7.86 15 .11  .4 1.1 MAA    2.2D  86 11 WW
2001 FEB  7 0811  6.00 38 49.46 122 48.51  4.38 29 .05  .2  .6 GEY    2.6D  55  7 WW
2001 FEB  7 0935 51.05 38 50.77 122 48.90  1.73 17 .03  .2  .6 GEY    2.3D  48  5 WW
2001 FEB  7 1359 39.02 36 39.75 121 17.24  7.51 72 .08  .1  .3 STN    3.1L  56  1 WW
 
2001 FEB  7 1440  4.69 36 39.53 121 16.98  7.20 43 .07  .2  .4 STN    2.5D  35  1 WW
2001 FEB  7 1442 48.18 36 39.53 121 17.01  7.21 40 .06  .2  .5 STN    2.2D  36  1 WW
2001 FEB  7 1451 19.67 36 39.48 121 16.97  6.83 33 .06  .2  .5 STN    2.1D  52  6 WW
2001 FEB  7 1515 51.12 36 39.57 121 17.00  7.52 66 .07  .1  .4 STN    3.0L  38  1 WW
2001 FEB  7 1822  8.76 36 39.94 121 17.55  7.91 74 .07  .1  .3 STN    3.8L  39  2 WW
 
2001 FEB  7 1919  2.04 40 34.76 124 27.16 22.50 26 .08  .7  .4 EUR    3.2L 223 15 WW
2001 FEB  7 2108 43.44 40 34.74 124 28.81 21.98 32 .10  .7  .5 EUR    3.2L 221 17 WW