Earthquake Hazards Program

Prepared in cooperation with the
California Geological Survey
and the
Southern California Earthquake Center

U.S. Geological Survey
Fact Sheet 2008-3027
version 1.0

Forecasting California’s Earthquakes—What Can We Expect in the Next 30 Years?

By Edward H. Field, Kevin R. Milner, and the 2007 Working Group on California Earthquake Probabilities


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In a new comprehensive study, scientists have determined that the chance of having one or more magnitude 6.7 or larger earthquakes in the California area over the next 30 years is greater than 99%. Such quakes can be deadly, as shown by the 1989 magnitude 6.9 Loma Prieta and the 1994 magnitude 6.7 Northridge earthquakes. The likelihood of at least one even more powerful quake of magnitude 7.5 or greater in the next 30 years is 46%—such a quake is most likely to occur in the southern half of the State. Building codes, earthquake insurance, and emergency planning will be affected by these new results, which highlight the urgency to prepare now for the powerful quakes that are inevitable in California’s future.

Download this report as a 4-page PDF file (fs2008-3027.pdf; 1.7 MB).

For questions about the content of this report, contact Ned Field

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Also of Interest

The Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2) USGS Open File Report 2007-1437/CGS Special Report 203/SCEC Contribution #1138

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