Tahoe temblor worthy of more study

Wednesday, Nov. 11, 1998 | 2:41 a.m.

The magnitude 4.9 earthquake on Oct. 30 is the latest example of the "significant seismic hazard" in the Lake Tahoe Basin, said Richard Schweickert, chairman of geological sciences at the school.

The quake that shook houses 30 miles away in Reno was centered on the north shore of the lake between Kings Beach, Calif., and Incline Village, Nev.

It has caused scientists reviewing new data to raise concerns about the extent of the threat in the basin from earthquakes, ground shaking, faulting, landslides and even seismic lake waves known as seiches.

Schweickert said additional geological and geophysical research in and around the lake is urgently needed to determine how often large earthquakes have occurred. That would help scientists better gauge the present-day hazard in the region, he said.

"We could be due for a big one right now, or it could be a few hundred years away," Schweickert said.

"There's nothing known about how many quakes have taken place (at Tahoe) or how frequently we can expect large earthquakes," he said.

Additional study of lake sediments and active faults on land should provide a history of the activity dating back as far as 10,000 years, he said.

Scientists mapping Lake Tahoe's bottom already have discovered evidence of large prehistoric quakes.

Those kinds of events "could cause major damage to dwellings and businesses and could disrupt transportation, communication and gas power lines," Schweickert said.

"Such seismic activity could have serious impacts on lake clarity and on the local economy. Major shaking could also affect the nearby Reno-Carson City metropolitan area," he said.