2000 North Coast Seismicity
2000 continued the relative seismic quiet on the North Coast since the mid 1990’s. Only nine earthquakes of magnitude 4 or larger were recorded, compared to 14 last year, the third lowest total since 1974. However two of those earthquakes were in the magnitude 5 range, the first since October of 1998. The largest earthquake of the year, a magnitude 5.9 on the morning of March 16, was felt by many in Humboldt County. Fortunately, the earthquake was far enough offshore to cause no damage. The magnitude 5.4 earthquake on January 7 was located too far offshore to be reported felt. Like last year, most of our earthquakes were located offshore - either along the Mendocino fault or within the Gorda plate.
2000 North Coast California Earthquakes of magnitude 4 or larger
(Northern Mendocino, Humboldt, Del Norte Counties)
DATE TIME LAT LONG ML MW LOCATION, COMMENTS
7-Jan. 6:17 PM 40.38 126.22 5.2 5.4 Gorda plate, 110 miles WSW Eureka.
15-Jan. 5:51 PM 40.46 125.71 4.3 4.3 Mendocino fault, 75 miles W Petrolia.
16-Mar 7:20 AM 40.39 125.28 5.8 5.9 Mendocino fault, 53 miles W Petrolia. Felt strongly in Petrolia-Ferndale-Honeydew area, felt from Point Arena to Redding and Gasquet.
2-Apr 10:06 PM 40.45 125.26 4.1 4.3 Mendocino fault, 52 miles W Petrolia.
4-May 5:31 AM 41.88 126.73 4.4 Gorda plate, 130 miles W Crescent City.
8-May 2:12 AM 40.32 124.69 4.2 4.5 Mendocino fault, 21 miles W Petrolia. Felt lightly in Petrolia.
13-Aug 11:17 AM 40.37 124.49 3.9 4.1 Southeastern Gorda plate, 11 miles WNW Petrolia. Felt lightly from Whitethorn to Eureka.
22-Sep 3:50 AM 40.86 124.45 4.4 4.5 Gorda plate, 16 miles WNW Eureka. Felt Petrolia to Patrick’s Point.
27-Dec 5:15 AM 40.47 124.47 4.0 4.1 Southeastern Gorda plate, 18 miles WNW Petrolia. Felt Westport to Trinidad.
Other felt earthquakes:
22-May 4:56 AM Mag. 3.3 20 miles SE of Eureka
6-July 5:15 PM Mag. 3.7 13 miles W of Petrolia
22-Sep. 11:27 AM Mag. 3.7 14 miles WNW Eureka, aftershock of mag 4.4 event.
9-Oct. 2:55 AM Mag. 3.6 0.5 miles NNE of Fortuna
25-Oct. 9:48 AM Mag. 3.5 60 miles WSW of Eureka
Note: All times/dates are local PST or PDT. ML is the Local or Richter magnitude as determined by the U.S. Geological Survey; MW is the moment magnitude as determined by the Berkeley Seismological Laboratory. The Moment magnitude is calibrated to agree on average with the Richter magnitude. For large earthquakes, the moment magnitude is considered a better measure of energy released. The felt areas of the more widely felt earthquakes are posted on the web at: http://pasadena.wr.usgs.gov/shake/
Compiled by Lori Dengler, Humboldt Earthquake Education Center, Department of Geology, Humboldt State University from data supplied by the U.S. Geological Survey and the Berkeley Seismological Laboratory. January 12, 2001.