Los Angeles might not end up as an island when the Big One rocks California, but any sizable seismic event on the San Andreas fault will send L.A. several meters closer to San Francisco. Scientists and the public have long expected a major quake to strike the West Coast; the U.S. Geological Survey estimates that California has a 99 percent chance before 2038 of experiencing at least a magnitude 6.7 quake—the same size as the 1994 Northridge earthquake.
But it could easily be bigger. Much bigger. If most of the San Andreas were to rupture in one event, an earthquake could reach a magnitude 8.2, says Lucy Jones, chief scientist of the Multi-Hazards Demonstration Project at the USGS in southern California.