Researchers say Lake Tahoe fault could deliver massive earthquake

SACRAMENTO - A fault line beneath Lake Tahoe could rupture at any time and unleash a massive earthquake that triggers an underwater landslide and sends 30-foot waves crashing into nearby parks, campgrounds, homes and marinas, researchers said.

Such an event along the West Tahoe Fault, the biggest of Lake Tahoe's three geologic faults, could also send waves over a dam that regulates water flow into the Truckee River, according to research presented last week at a meeting of the American Geophysical Union in San Francisco.

The West Tahoe Fault, which skirts the lake's western shore and runs through Fallen Leaf Lake and beyond to the south, is large enough to deliver a temblor of magnitude 7 or higher, according to the researchers.

However, it's unclear when a large quake might strike. The last big earthquake along the fault appears to have occurred between 4,000 and 6,000 years ago, and the fault appears to produce major earthquakes every 5,000 to 7,000 years, according to the researchers.

Several more years of research is needed to determine the likelihood of a major earthquake on Lake Tahoe, according to the scientists from three universities - University of California, San Diego; San Diego State University; and the University of Nevada, Reno - who are conducting the research. They have conducted much of their research using a boat and a laboratory operated by the University of California at Davis.

Their research is designed to better understand the history of Lake Tahoe's earthquakes and the volatility of its fault lines.

The findings will likely make their way onto federal earthquake hazard maps that help determine building codes and set insurance rates.

"We're keeping an eye on it," said Michael Reichle, chief seismologist at the California Geological Survey. "There are active faults near the lake, under the lake and to the east in Nevada at the base of the hills. We still don't know very much about all those faults."