May 30, 2008—California has more than a 99 percent chance of having a magnitude 6.7 or larger earthquake within the next 30 years, according to scientists using a new model to determine the probability of big quakes.
The likelihood of a major quake of magnitude 7.5 or greater in the next 30 years is 46 percent-and such a quake is most likely to occur in the southern half of the state, says the study.
The new study determined the probabilities that different parts of California will experience earthquake ruptures of various magnitudes. The new statewide probabilities are the result of a model that comprehensively combines information from seismology, earthquake geology, and geodesy (measuring precise locations on the Earth’s surface). For the first time, probabilities for California having a large earthquake in the next 30 years can be forecast statewide.
The new information is being provided to decision makers who establish local building codes, earthquake insurance rates, and emergency planning and will assist in more accurate planning for inevitable future large earthquakes.
The official earthquake forecasts, known as the “Uniform California Earthquake Rupture Forecast (UCERF),” were developed by a multidisciplinary group of scientists and engineers, known as the Working Group on California Earthquake Probabilities. Building on previous studies, the Working Group updated and developed the first-ever statewide, comprehensive model of California.
The organizations sponsoring the Working Group include the US Geological Survey, the California Geological Survey and the Southern California Earthquake Center. An independent scientific review panel, as well as the California and National Earthquake Prediction Evaluation Councils, have evaluated the new UCERF study.
For more information, see the Web site of the Southern California Earthquake Center.
