Working group for California's earthquake report includes UO's Weldon

EUGENE, Ore. -- (April 14, 2008) -- University of Oregon geologist Ray Weldon is a member of the working group that created the Uniform California Earthquake Rupture Forecast (UCERF) that was released today. The group's study projects a more than 99 percent chance of a magnitude 6.7 or larger earthquake striking California within the next 30 years.

Under the new model, there is a 10 percent chance for a major magnitude 8 to 9 earthquake in the 750-mile Cascadia Subduction Zone during the same period, Weldon said.

The official news release is available at the Web site of the U.S. Geological Survey (USGS) Newsroom.

The Cascadia zone primarily is off the Oregon coast and extends about 150 miles into California. Such quakes occur about once every 500 years on average. The zone stretches from mid-Vancouver Island to Northern California and separates the Juan de Fuca and North America plates. The new model does not estimate the seismic hazard that would be caused by such quakes.

The official earthquake forecasts 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 newly announced model was built using a variety of new techniques and new data, all of which were incorporated into the new USGS's National Seismic Hazard Map. The map, which is to be released later, includes coordinated methodology for consistency beyond California, Weldon said.

The revised National Seismic Hazard Map is being provided to decision-makers who establish building codes and earthquake insurance rates and to emergency planners. The revisions, Weldon said, may lead to changes in Oregon.

"The Working Group's model will be used to set earthquake insurance rates in California, which will certainly affect rates in Oregon," said Weldon, who in May 2006 was one of 12 U.S. scientists named to the U.S. Geological Survey's National Earthquake Prediction Evaluation Council in addition to his role on the Working Group. "The National Seismic Hazard Map also will be used to set building codes, including in Oregon."

The organizations sponsoring the Working Group include the U.S. Geological Survey, the California Geological Survey and the Southern California Earthquake Center.

Additional information is available via the Web:

• The full UCERF report
• Summary fact sheet