California faces 99.7 percent chance of big quake in next 30 years

LOS ANGELES " California " land of sun, beaches and earthquakes " faces an almost certain risk of being rocked by a strong temblor by 2037, scientists said Monday in the first statewide forecast of the seismic threat.

New calculations reveal there is a 99.7 percent chance a magnitude 6.7 quake or larger will hit the Golden State 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.

Despite the new results, scientists still cannot predict exactly where in the state such a quake will occur or when. But they say it should be a wake-up call for residents to prepare for a natural disaster in earthquake country.

The latest analysis is the first comprehensive effort by the USGS, SCEC 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.

Given California's seismic history, the new results should come as no surprise, said David Schwartz, a USGS geologist in Menlo Park who was not part of the study.

Of all the faults in the state, the southern San Andreas, which runs from Parkfield to the Salton Sea, appears most primed to break, scientists found. There is a 59 percent chance in the next three decades that a Northridge-size quake will occur on the fault compared to 21 percent for the northern section.

The northern San Andreas produced the 1906 San Francisco earthquake, a recent disaster in geologic time compared to the southernmost segment, which has not popped in more than three centuries.

Scientists are also concerned about the Hayward and San Jacinto faults, which have a 31 percent chance of producing a Northridge-size temblor in the next 30 years. The Hayward fault runs through densely populated cities in the San Francisco Bay Area. The San Jacinto fault bisects the fast-growing city of San Bernardino.

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On the Net:

U.S. Geological Survey: http://www.usgs.gov

Southern California Earthquake Center: http://www.scec.org

California Geological Survey: http://www.conservation.ca.gov/cgs/Pages/Index.aspx