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USGS Forecast: Chances Of Magnitude-8 Earthquake Up 7 Percent

LOS ANGELES ( — The good news is there's less of a chance of a magnitude-6.7 earthquake hitting California in the coming years, but the bad news is the likelihood of a magnitude-8 or larger hitting in the next 30 years has jumped from 4.7 percent to 7 percent.

The new forecast was released Tuesday by the U.S. Geological Survey.

"The new likelihoods are due to the inclusion of possible multi-fault ruptures, where earthquakes are no longer confined to separate, individual faults, but can occasionally rupture multiple faults simultaneously," according to USGS scientist Ned Field. "This is a significant advancement in terms of representing a broader range of earthquakes throughout California's complex fault system."

In 2008, the USGS estimated that quakes of about magnitude-6.7 – the size of the 1994 Northridge quake – were expected to hit the state once every 4.8 years. The latest report estimates one such quake every 6.3 years.

The 2008 report found that the likelihood of a magnitude-8 or larger quake hitting in the next 30 years was 4.7 percent. The new report puts the likelihood at 7 percent.

"We are fortunate that seismic activity in California has been relatively low over the past century," according to Tom Jordan, director of the Southern California Earthquake Center. "But we know that tectonic forces are continually tightening the springs of the San Andreas fault system, making big quakes inevitable."

(©2015 CBS Local Media, a division of CBS Radio Inc. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. Wire services contributed to this report.)

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