Tsunami threat to Tahoe analyzed by seismologists

Sunday, April 9, 2000 | 3:47 a.m.

By analyzing an adjacent fault five miles from Tahoe, researchers learned how such a magnitude-7 quake would create waves as high as 30 feet, threatening shoreline houses, businesses and roadways.

A major temblor similar to ones that have rocked Tahoe about once every 1,500 years would create a huge wave known as a tsunami, followed by other waves, they say.

UNR Seismological Laboratory Director John Anderson and doctoral student Gene Ichinose will present new research on Tahoe's seismic hazards in the April 15 edition of the Geophysical Research Letters journal.

Ichinose said researchers are unsure of the probability of a 7-magnitude quake occurring under the Sierra lake famous for its clear, blue waters.

"We can't go to the bottom of the lake and sample the faults," he said. "But by looking at the adjacent Genoa fault, I'd say one reasonable estimate would be a 3 to 4 percent chance of that happening in the next 50 years.

"This is a much lower probability than the occurrence of a devastating forest fire or flood. Nevertheless, shoreline residents should be aware of the danger and move to high ground in the event of a large earthquake."

The 30-foot waves would crash Tahoe's shoreline in a few places where wave energy is focused, according to the researchers. Almost the entire shoreline could experience 10-foot waves.

Last month, UNR seismologists said new historical evidence indicates a 7-magnitude quake could cause other major damage at Tahoe, ranging from collapsed buildings to avalanches and forest fires.

New research has found a number of previously undisclosed faults, including one suspected of causing a 4.9-magnitude temblor that shook Tahoe last October.