<P> The San Andreas Fault System has been the subject of a flood of studies . In particular, scientific research performed during the last 23 years has given rise to about 3,400 publications . </P> <P> A study published in 2006 in the journal Nature found that the San Andreas fault has reached a sufficient stress level for an earthquake of magnitude greater than 7.0 on the moment magnitude scale to occur . This study also found that the risk of a large earthquake may be increasing more rapidly than scientists had previously believed . Moreover, the risk is currently concentrated on the southern section of the fault, i.e. the region around Los Angeles, because massive earthquakes have occurred relatively recently on the central (1857) and northern (1906) segments of the fault, while the southern section has not seen any similar rupture for at least 300 years . According to this study, a massive earthquake on that southern section of the San Andreas fault would result in major damage to the Palm Springs - Indio metropolitan area and other cities in San Bernardino, Riverside and Imperial counties in California, and Mexicali Municipality in Baja California . It would be strongly felt (and potentially cause significant damage) throughout much of Southern California, including densely populated areas of Los Angeles County, Ventura County, Orange County, San Diego County, Ensenada Municipality and Tijuana Municipality, Baja California, San Luis Rio Colorado in Sonora and Yuma, Arizona . Older buildings would be especially prone to damage or collapse, as would buildings built on unconsolidated gravel or in coastal areas where water tables are high (and thus subject to soil liquefaction). The paper concluded: </P> <P> The information available suggests that the fault is ready for the next big earthquake but exactly when the triggering will happen and when the earthquake will occur we cannot tell (...) It could be tomorrow or it could be 10 years or more from now . </P> <P> Nevertheless, in the 12 years since that publication there has not been a substantial quake in the Los Angeles area, and two major reports issued by the U.S. Geological Survey (USGS) have made variable predictions as to the risk of future seismic events . The ability to predict major earthquakes with sufficient precision to warrant increased precautions has remained elusive . </P>

Summary of the history of san andreas fault