California Earthquake Forecast – Update 3

For background and latest update see:

• California Earthquake Forecast – Update 2 [August 11, 2009 ]
• California Earthquake Forecast 2009 – UPDATE [August 4, 2009]
• California Earthquake Forecast 2009 [March 24, 2009]

• California Earthquake Forecast – Update 4  [April 12, 2010]

Up to three earthquakes measuring magnitude 6.2 or greater could strike Western US in 2009

California Earthquake Forecast: UPDATE #3

Magnitude 7.6  to  7.9 earthquake could strike the SF Bay Area, northern California in 2009

FEWW Moderators Forecast a magnitude 7.6 to 7.9  earthquake and two possible aftershocks measuring about 5.5 Mw (subject to the magnitude of the mainshock) for the San Francisco Bay Area, northern California in 2009.

Details of EQ Forecast

• Magnitude: 7.6 to 7.9 Mw

• Provisional date:  September 28, 2009
• Date uncertainty: ~ 90 Days
• Epicenter: 37° 52′ 20″N, 122° 15′ 10″W
• Depth: 9.0 km
• Depth uncertainty: ±2.8 km
• Location: ~2.88 km (1.79miles ) east of Berkeley Fire Departments: Fire Prevention & Disaster Preparedness (CA 94702).
• Location uncertainty:
  • Up to 5 km to the west of Hayward Fault
  • Up to 14 km NNW within a 5-km corridor along the Hayward Fault
  • Up to 22 km SSE within a 5-km corridor along the Hayward Fault

• Probability of of occurrence 0.8 [77%]

Map of N California Fault Lines. Source: USGS

Satellite map of forecast epicenter. Source: Google Maps [See terms of use for copyright information.]

FEWW Bay Area Earthquake Forecast Uncertainty Zone. Source: Google Earth [See terms of use for copyright information.]

Note: This forecast does NOT preclude the possibility of other seismic events in the area at any time.

Related Links:

• FEWW Earthquake Links
• California Earthquake Forecast – Update 2 [August 11, 2009 ]
• California Earthquake Forecast 2009 – UPDATE [August 4, 2009]
• California Earthquake Forecast 2009 [March 24, 2009]

California Earthquake Forecast – Update 2

California forecast earthquake may be more powerful than originally estimated

FEWW Moderators have upgraded their forecast for a California earthquake to a Magnitude 7.9 event.

For initial forecast see California Earthquake Forecast 2009 [March 24, 2009]

For Update # 1 see:  California Earthquake Forecast 2009 – UPDATE [August 4, 2009]

San Andreas Fault

The topographic texture of western California is controlled by the San Andreas fault system, the tectonic expression of the Pacific plate sliding northwestward along the western margin of the North American plate. Hundreds of miles long and up to a mile wide, the San Andreas Fault Zone has been active since its original development in the Tertiary.  About 10 percent of the present plate motion is compressional, which means horizontal forces are shortening and wrinkling the crust along the fault zone. This movement has created the parallel coastal northwest-southeast mountain ranges such as the Coastal Ranges along California’s central coast. Comparatively quiet during the period between the 1906 San Francisco earthquake and the 1989 Loma Prieta event, the fault is again showing activity. Image and caption: nationalatlas.gov

Fault map for San Francisco Bay Area from http://www.abag.ca.gov/bayarea/eqmaps/pickcity.html, annotated and colors modified by User: Leonard G. Released into the public domain (Leonard G. ).

Related Links:

• California Earthquake Forecast 2009
• California Earthquake Forecast 2009 – UPDATE
• FEWW Earthquake Links

California Earthquake Forecast 2009 – UPDATE

For initial forecast see:

California Earthquake Forecast 2009

Based on the recent seismic activity in the Gulf of California, FEWW Moderators revise their forecast for California earthquakes in 2009 as follows:

(i) A magnitude 7.4 earthquake and two strong aftershocks (5.5+ Mw) could strike California in 2009 with a probability of 0.9 (88%).

(ii) The estimated date of occurrence:  September 28, 2009

(iii) The occurrence date uncertainty: ~ +90 days from the forecast date

(iv) The epicenter is located in a built-up area. [Further information may be released later.]

(v) In addition to the above event, two other powerful earthquakes could strike the western United States in 2009.  (Probability of occurrence for a  single event is 77% and for the two events, 64%).

Related Links:

• California Earthquake Forecast 2009
• Earthquakes