August 2006 Commentary

A major earthquake was recorded with an epicenter located about 8400 miles SE of Berkeley, in the Scotia Sea, about 300 miles WSW of Bristol Island in the South Sandwich Islands. The moment magnitude of this earthquake was 7.0. You can view the USGS info on this earthquake here. You may view the Harvard moment tensor solution, as well.

A moderate earthquake was recorded with epicenter located about 3 miles W of Glen Ellen and 9 miles SE of Santa Rosa, CA. The moment magnitude (Mw) for this event is 4.4. The earthquake was reported felt as far north as Ukiah, south to beyond San Jose, and east beyond Sacramento. The maximum Modified Mercalli Intensity was V. See the Instrumental Intensity map and the Community Internet Intensity map. The San Francisco Chronicle filed this report. As noted in the article, this epicenter lies two miles NE of the Rodgers Creek Fault, and the moment tensor solution indicates motion along a plane with strike quite different from that of this fault. Therefore this earthquake is assumed to have occurred on a smaller, separate fault which has not yet been determined. The event did trigger the longest rod on our "Falling Pin Seismometer" (donated by Dale Johnson of the Class of '45).

Two small aftershocks closely followed the main event: a magnitude 2.0 quake at 09:09 PM, and a magnitude 1.5 event at 09:25 PM PDT.