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Giant Quakes May Have Occurred in California - Delta ISB Member Sees Japanese Temblor as Reminder of North American Risk

April 2011

California has a history of quakes as large as the giant 9.0 off the coast of northern Honshu, Japan. That’s according to Delta Independent Science Board Member Brian Atwater, whose expertise includes studying ancient earthquakes and tsunamis.

“Earthquake forecasting is more practical than earthquake prediction,” said Dr. Atwater.

Earthquake forecasts in California are based, in part, on the state’s history of quakes. Dr. Atwater points to earthquake history inferred from North American geology and Japanese documents. Together this evidence tells of a giant earthquake in A.D. 1700 along the North America’s largest active fault outside Alaska – a fault that extends 700 miles from Vancouver Island in British Columbia to Cape Mendocino in Humboldt County. How this quake and its predecessors were discovered can be seen in “The Orphan Tsunami of 1700” here.

The source area of the 1700 quake is more than 200 miles from the legal Delta. But that’s close enough for seismologists to use it as they try to forecast future shaking of the Delta’s levees. They also consider quake sources in the Bay Area and beneath the Delta itself.

To read an in-depth interview with Dr. Atwater on this subject, check out the April issue of Science News, the Delta Science Program’s bimonthly online newsletter.

USGS Simulated Tsumani

Coequal goals

The Delta Stewardship Council was created in legislation to achieve the state mandated coequal goals for the Delta. "'Coequal goals' means the two goals of providing a more reliable water supply for California and protecting, restoring, and enhancing the Delta ecosystem. The coequal goals shall be achieved in a manner that protects and enhances the unique cultural, recreational, natural resource, and agricultural values of the Delta as an evolving place." (CA Water Code §85054)