Researchers warn of Tahoe quake potentials

Friday, March 26, 1999 | 9:43 a.m.

"We have faults that are capable of very large earthquakes in the Tahoe Basin said Ken Smith, a seismologist at the University of Nevada, Reno.

Smith and other researchers briefed Tahoe Regional Planning Agency governors on Wednesday and urged them to support further studies on the danger of quakes at the lake.

Research has found a number of previously undisclosed faults, including one suspected of causing the magnitude 4.9 quake that shook the area last October.

Recent underwater mapping conducted by the U.S. Geological Survey also proved suspicions that massive landslides triggered by quakes occurred on the west side of Lake Tahoe, scattering boulders and chunks of dirt on the lake's bottom.

The largest slide in the area of McKinney Bay is believed to have been triggered by a magnitude 7 quake that occurred within the last 10,000 years, scientists said.

"We have very compelling evidence of enormous, catastrophic slide events," said Richard Schweickert, chairman of geological sciences at UNR.

And if large quakes and landslides occurred in the past, there's every reason to believe they will occur again, he said.

Experts say a modern quake of magnitude 7 could cause widespread damage, ranging from collapsed buildings to avalanches, tsunamis and forest fires.

UNR researchers also worry about the retention dam at Tahoe City, Calif., which allows storage of the top six feet of lake water as a reservoir.

The dam was built in 1913, and experts fear damage from a large quake could cause severe flooding along the Truckee River.

The scientists said further geological and earthquake hazard and emergency safety studies are needed for the region.

Until more is known, the true danger of quakes in the Tahoe Basin cannot be determined, Smith said.

"We don't know what the recurrences are and when to expect them," he said.