Quake map shows faults | TahoeDailyTribune.com

Quake map shows faults

Emily Aughinbaugh, Tribune staff writer

A newly released map of Lake Tahoe’s fault lines shows the basin has greater potential for earthquake activity than originally believed.

Scientists from the Department of Geological Sciences at the University of Nevada, Reno and the Nevada Seismological Laboratory, released the map in November as a work-in-progress after using aerial photography, topographic maps, digital topography and field observations to interpret active faults and tectonics in the basin.

Dr. Richard Schweickert, professor of geology at UNR and one of the project’s scientists, said researchers found three active fault zones, meaning they have produced earthquakes within the last 10,000 years.

Schweickert said one of the faults runs northeast from the deepest part of Lake Tahoe at the north end through Incline Village and over Mount Rose.

Another line runs north-south along the West Shore, and the third fault, called the Tahoe Sierra Frontal, runs through the mountains just west of the lake.

Jim Howle, another researcher and geologist at UNR, said the group was able to discover new active faults at the bottom of the lake.

Howle said more research needs to be done on predicting the recurrence intervals of earthquakes resulting from these faults, but said lake residents should still be aware of the faults existence.

“I think there’s a lot of complacency because there hasn’t been earthquakes in the basin in recent times,” Howle said. “These previously unknown faults at the bottom of the lake are active and capable of producing large earthquakes.”

Howle said the faults at the bottom of Lake Tahoe are capable of producing magnitude 7 temblors, however Schweickert said more research needs to be done in order to determine whether the quakes are likely.

“There’s a lot of evidence that points to the occurrence of large earthquakes,” Schweickert said. “We don’t want to say these things are very likely to happen. Our goal is to see if we can determine when the last event was and then figure out (the earthquakes’) timing.”

Geological science researchers formulated a model in the Nevada Seismological Laboratory at UNR to study what would happen if a Magnitude 7 quake occurred at the bottom of the lake or at the basin.

Scientists concluded large temblors at the bottom of the lake would have hazardous affects on California and Nevada lakeside communities, generating tsunami-type waves ranging in height from 9 feet to 33 feet.

However, fault ruptures outside of the lake basin would only produce waves a little over a foot and a half.

Quakes felt around South Shore

n November 2000, Magnitude 2.4, originated 12 miles west of Reno on the California-Nevada line

n September 2000, Magnitude 4.7, originated two miles southeast of Topaz Lake, Nev.

n 1998, Magnitude 4.9, originated in Incline

n 1994, Magnitude 6, originated in Gardnerville with several aftershocks of Magnitude 4.5

Source: Ken Smith, seismologist, University of Nevada, Reno

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