M4.7 Anza Earthquake - 3/11/13 9:56AM
CISN/SCSC Executive Summary (E. Hauksson, L. Jones, D. Given, K. Hutton, A. Guarino, N. Scheckel, R. Dollar, R. Graves, and K. Hudnut)
Anza- A M4.7 earthquake occurred at 9:56AM PDT on March 11, 2013, located 12 miles ESE of Anza, CA, 23 miles south of Palm Springs, CA. The event was felt throughout Southern California, from the US/Mexico border north to Santa Barbara. As of 3/19/13, there have been 9,930 felt reports submitted so far. Felt reports were submitted at http://earthquake.usgs.gov/earthquakes/eventpage/ci15296281#dyfi.
The event was preceeded by four small foreshocks within a span of two minutes of the mainshock. The event occurred in the San Jacinto Fault zone, a large fault zone that extends from the southern part of the state, just west of the Salton Sea, north near the Cajon Pass. This fault system produces more earthquakes than any other fault in Southern California, and has produced eight M6.0 or larger events in the past 100 years. This is the sixth event larger than M4.7 in the past 20 years.
This event has produced a very robust aftershock sequence, with approximately 90 aftershocks within 90 minutes of the mainshock. Aftershocks are continuing, and the total number of aftershocks have exceeded 1,000 so far, and as more analysis continues, more events will be added.
Earthquake Early Warning Update - ShakeAlert:
The ShakeAlert demonstration earthquake early warning system detected this event and sent notifications to test users. The EEW system is still in beta test mode, but was a success with this event.
The map above shows felt reports submitted to Caltech/USGS via the "Did You Feel It?" website, located at http://earthquake.usgs.gov/earthquakes/eventpage/ci15296281#dyfi.
Since 2001, there have been two other Anza earthquakes that have occurred in this area, and the scsn.org special reports may be found at:
2001 M5.1 Anza Earthquake: http://www.scsn.org/2001anza.html
2005 M5.2 Anza Earthquake: http://www.scsn.org/2005anza.html