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@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
The largest event to occur this week in this region was a light earthquake of magnitude 4.0 8 miles NNE of Fort Bragg, CA at 03:34 PM UTC Sunday, Jan 24, 1999 (07:34 AM PST Sunday, Jan 24, 1999).
This earthquake occurred adjacent to, but not on the San Andreas fault. The focal mechanism indicates reverse motion rather than strike slip.
The largest event to occur this week in this region was a minor earthquake of magnitude 3.8 9 miles N of Morgan Hill, CA at 03:58 AM UTC Wednesday, Jan 27, 1999 (07:58 PM PST Tuesday, Jan 26, 1999).
This earthquake occurred on the Calaveras fault in the aftershock zone of the 1984 Morgan Hill M6.2 earthquake on a section of the fault with recurring minor seismicity.
The largest event to occur this week in this region was a microearthquake of magnitude 2.9 6 miles W of Toms Place, CA at 09:46 AM UTC Friday, Jan 22, 1999 (01:46 AM PST Friday, Jan 22, 1999).
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 N RMS ERH ERZ LOC PREF YR MON DA HRMN SEC DEG MIN DEG MIN KM RD S SEC KM KM REMKS MAG 99 JAN 21 1103 19.78 38 47.91 122 46.26 1.14 10 .02 .2 .6 GEY 2.1D 99 JAN 21 2342 22.63 40 42.29 122 23.18 20.52 16 2 .29 1.5 1.0 SHA # 2.2D 99 JAN 22 135 51.00 38 47.25 122 45.99 0.83 15 .04 .2 .5 GEY 2.5D 99 JAN 22 225 5.25 37 34.28 118 47.10 7.86 18 .06 .4 .6 MOR 2.4D 99 JAN 22 656 50.81 38 48.19 122 45.17 1.41 26 1 .04 .1 .3 GEY 2.5D 99 JAN 22 946 52.72 37 34.35 118 47.05 8.46 24 1 .05 .3 .5 MOR 2.9D 99 JAN 22 2038 15.44 37 17.51 121 40.05 6.13 68 2 .04 .1 .2 SFL 2.2D 99 JAN 23 1424 0.21 37 38.16 119 21.55 20.19 29 .07 .3 .7 KAI 2.6D 99 JAN 23 1424 2.76 37 32.40 119 10.14 0.40 16 .17 1.212.2 KAI - 2.2D 99 JAN 23 2303 53.78 37 18.00 119 58.47 15.32 37 2 .26 .3 .4 KAI 2.5D 99 JAN 24 448 14.10 36 32.91 121 8.35 6.80 41 .04 .1 .4 PIN 2.3D 99 JAN 24 928 37.36 38 48.49 122 47.90 2.29 29 .06 .2 .3 GEY 2.8D 99 JAN 24 1040 55.70 36 48.96 121 32.19 4.64 45 .14 .2 .4 SJB 2.1D 99 JAN 24 1132 26.64 40 44.76 124 28.40 19.69 19 .06 .7 .7 EUR 2.1D 99 JAN 24 1534 56.55 39 33.45 123 46.29 5.57 43 1 .24 .4 .6 PAR 4.0L 99 JAN 24 2353 29.82 37 50.61 122 3.39 14.06 67 1 .11 .1 .3 CON 2.2D 99 JAN 25 107 58.80 39 33.60 123 45.09 0.76 29 2 .06 .3 1.7 PAR 2.4D 99 JAN 25 304 49.85 37 32.09 118 51.47 9.41 20 .04 .3 .6 MOR 2.1D 99 JAN 25 1638 59.46 39 36.02 122 4.42 12.41 66 .25 .3 .6 SAC 2.9D 99 JAN 26 746 4.06 38 50.02 122 47.93 1.85 22 .04 .2 .6 GEY 2.1D 99 JAN 26 901 50.13 38 49.23 122 46.74 1.56 34 .03 .1 .2 GEY 2.6D 99 JAN 26 1623 49.94 37 31.06 118 48.72 1.67 12 .03 .4 8.1 MOR - 2.2D 99 JAN 27 231 30.21 38 48.72 122 48.39 1.43 18 .05 .2 .4 GEY 2.1D 99 JAN 27 358 42.89 37 15.20 121 38.29 6.32 93 .06 .1 .3 SFL 3.8L 99 JAN 27 1242 2.58 37 36.59 118 51.50 5.32 23 .07 .3 .3 SMO 2.4D
