SAN FRANCISCO
05/30/2012 07:16 pm ET

New Earthquake Faults Discovered West Of Lake Tahoe

Californians may be unfazed by the knowledge that their state is one of the most seismically active regions in the world, but the addition of even more potential danger can't be good for those awaiting the next "big one."

Scientists studying earthquakes in the mountains west of Lake Tahoe have found new seismic faults--and they may be hazardous. The largest of their new discoveries is a 22-mile-long strike-slip fault named Polaris for the old mining town it runs through.

The fault range could generate strong earthquakes with magnitudes from 6.3 to 6.9, according to the U.S. Geological Survey, but because the fault connects to others in the area, the magnitude could be even higher if they ruptured at the same time. Temblors along the fault could also trigger landslides along the entire Tahoe-Sierra line, which stretches from Truckee to South Lake Tahoe.

"We weren't expecting it at all," said Lewis Hunter, a senior geologist for the U.S. Army Corps of Engineers Sacramento District, told Our Amazing Planet.

Scientists worry that activity from the new fault could lead to the rupture of a nearby dam and subsequent flooding of the area. Since Martis Creek Dam is already known to be in an active fault zone, the water levels are kept as low as possible. However, because the Polaris sits between the dam and its spillway, if the water levels were higher than usual, a very big earthquake could potentially flood a portion of Reno.

The new faults have been discovered thanks to technology developed by a coalition of University of Nevada-Reno, UC Berkeley and Army Corps Engineers. The bare-earth airborne LiDAR offers a look at tectonic activity usually obscured by vegetation.

"This study is yet one more stunning example of how the availability of LiDAR information to precisely and accurately map the shape of the solid Earth surface beneath vegetation is revolutionizing the geosciences," USGS Director Marcia McNutt told the Sacramento Bee.

Although the team established that the most recent earthquake caused by the Polaris fault was 15,000 years ago, the time period remains well within the 35,000 years used to define an active fault.

"We feel very confident it's within our range for being active," Dr. Hunter said.

Scientists believe there may be hundreds of unknown faults around the world.

CONVERSATIONS