Published on 16 Feb 2015 | about 1 year ago
The San Andreas Fault is a continental transform fault that extends roughly 810 miles through California. It forms the tectonic boundary between the Pacific Plate and the North American Plate, and its motion is right-lateral strike-slip (horizontal). The fault divides into three segments, each with different characteristics and a different degree of earthquake risk, the most significant being the southern segment, which passes within about 35 miles of Los Angeles.
A study in 2006 concluded that the San Andreas fault has reached a sufficient stress level for the next "big one", or a M ≥ 7.0, to occur. It also concluded that the risk of a large earthquake may be increasing more rapidly than researchers had previously thought. The paper stated that, while the San Andreas Fault had experienced massive earthquakes in the central (1857) and northern (1906) segments, the southern section of the fault has not seen any similar rupture for at least 300 years. Such an event would result in substantial damage to Palm Springs and other cities in San Bernardino, Riverside and Imperial counties in California, and Mexicali municipality in Baja California. It would be felt throughout much of Southern California, including densely populated areas of San Bernardino, Los Angeles, Orange County, San Diego, Ensenada and Tijuana, Baja California, San Luis Rio Colorado in Sonora and Yuma, Arizona.
As both the public and scientific community continue to speculate on the size of the next earthquake to strike California, predicting major earthquakes with sufficient precision to warrant taking increased precautions has long been sought but remains elusive. Nonetheless, the 2008 Uniform California Earthquake Rupture Forecast (UCERF) has estimated that the probability of an M ≥ 6.7 earthquake within the next 30 years on the northern and southern segments of the San Andreas fault is somewhere between 21% and 59%, respectively.