Monday, December 25, 2006

Tahoe Fault

The technology that discovers these cracks in the earth and provides the means to perhaps do something about protecting ourselves from their rupture, is a real blessing, if used to properly to plan mitigation rather than making decisions in panic mode.

Tahoe fault raises red flag
Potential for a lake tsunami discovered with aid of UCD research sub
By Carrie Peyton Dahlberg - Bee Staff Writer
Published 12:00 am PST Monday, December 25, 2006

The biggest fault beneath Lake Tahoe could be due to rupture any time, according to a new evaluation being prepared by researchers who probed Tahoe and nearby Fallen Leaf Lake earlier this year.

The preliminary conclusions, outlined last week at a meeting of the American Geophysical Union in San Francisco, help sharpen a still blurry picture of potentially tsunami-spawning faults that lurk beneath the lake.

Ultimately, the findings will make their way into federal earthquake hazard maps that help determine building codes and set insurance rates.

"We have been looking at Tahoe as one of the biggest changes for California" in new maps due out in late 2007, said Mark Petersen, chief of the national seismic hazard project at the U.S. Geological Survey in Colorado.

What's become clearer with the latest Tahoe expeditions, supported by a UC Davis research vessel and led by scientists from three universities, is both the size and the potential of the West Tahoe Fault.

The fault, which skirts the lake's west shore, runs all the way through Fallen Leaf Lake and beyond to the south, said Graham Kent, a research geophysicist at UC San Diego's Scripps Institution of Oceanography.

While that didn't surprise Kent, it confirms that the fault is Tahoe's "800 pound gorilla," long enough to deliver a big jolt, magnitude 7 or more.

Such a quake could trigger an underwater landslide that quickly displaces huge amounts of water, potentially sending giant waves surging into parks, campgrounds, homes and marinas along the lake's shore, and possibly overtopping a dam that regulates flow into the Truckee River.