The Marina district disaster zone after an earthquake, measuring 7.1 on the richter scale on Oct. 17, 1989 in San Francisco.
Otto Greule Jr—Getty Images
By Jack Linshi
March 10, 2015

The chances of earthquake magnitude 8.0 or greater hitting California in the next 30 years have been increased from about 4.7% to 7%, the U.S. Geological Survey (USGS) said in a statement Tuesday.

The revised forecast was calculated by the Third California Earthquake Rupture Forecast (UCERF3), a follow-up to 2008’s UCERF2 conducted by USGS and its partners, who modeled the latest geological data.

While UCERF3 increased the odds of a massive California earthquake, the study lowered the chance of an earthquake around magnitude 6.7—like the 1994 Northridge earthquake—by about 30%, from one every 4.8 years to one every 6.3 years.

“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,” said the study’s lead author Ned Field.

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