Big Quake to Rock Calif. by 2037

April 14, 2008 -- California faces an almost certain risk of being rocked by a strong earthquake by 2037, scientists said Monday in the first statewide temblor forecast.

New calculations reveal there is a 99.7 percent chance a magnitude 6.7 quake or larger will strike in the next 30 years. The odds of such an event are higher in Southern California than Northern California, 97 percent versus 93 percent.

The last time a jolt this size rattled California was the 1994 Northridge disaster, which killed 72 people, injured more than 9,000 and caused $25 billion in damage.

"It basically guarantees it's going to happen," said Ned Field, a seismologist with the U.S. Geological Survey in Pasadena and lead author of the report.

California is one of the most seismically active regions in the world. More than 300 faults crisscross the state, which sits atop two of Earth's major tectonic plates, the Pacific and North American plates. About 10,000 quakes each year rattle Southern California alone, although most of them are too small to be felt.

The analysis is the first comprehensive effort by the USGS, Southern California Earthquake Center and California Geological Survey to calculate earthquake probabilities for the entire state using newly available data. Previous quake probabilities focused on specific regions and used various methodologies that made it difficult to compare.

For example, a 2003 report found the San Francisco Bay Area faced a 62 percent chance of being struck by a magnitude 6.7 quake by 2032. The new study increased the likelihood slightly to 63 percent by 2037. For the Los Angeles Basin, the probability is higher at 67 percent. There is no past comparison for the Los Angeles area.