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NR 2005-08
April 26, 2005

Contact: Ed Wilson
Mark Oldfield
Don Drysdale
(916) 323-1886

DEPT. OF CONSERVATION’S CALIFORNIA GEOLOGICAL SURVEY ISSUES EARTHQUAKE SHAKING POTENTIAL MAP FOR RENO-TAHOE

INCLINE VILLAGE, Nev. – California and Nevada share more than just a border. They share faults. A map unveiled by the Department of Conservation’s California Geological Survey today shows earthquake shaking potential in the Reno-Tahoe area.

“The seismic hazard in the Tahoe area is related to faults on both sides of the California-Nevada border, which is why we’re involved,” said California State Geologist John Parrish, head of CGS. “Fault lines don’t care about state lines. We’re happy to work with our partners in this growing region of Nevada.”

The map covers Washoe, Storey, Carson City, Douglas, Lyon, Churchill and Mineral counties in Nevada, as well as parts of Nye and Esmeralda counties. Also included are all or parts of the following California counties: Lassen, Plumas, Sierra, Nevada, Placer, El Dorado, Amador, Alpine, Calaveras, Tuolumne, Mono, Mariposa, Madera, Fresno, Stanislaus, Merced and Inyo.

Areas of Nevada just south of the Reno-Sparks area and in the Fish Lake Valley are among the most likely to receive strong shaking during a large earthquake, according to the map.

The map also indicates a high level of shaking potential along the Genoa fault from just south of Reno-Sparks through Carson City through the Minden-Gardnerville area to just north of Markleeville in California. High shaking potential is also shown in the Mono and Mammoth lakes areas due to active faults and soil amplification, and in the area around Dyer, Nev., at the northern end of the Death Valley fault system.

The map shows shaking that has a 10 percent chance of occurring in a 50-year period, according to Chris Wills, the CGS Supervising Geologist who oversaw the mapping project. The California Building Code specifies critical structures such as schools and hospitals be able to withstand the highest anticipated levels of shaking. Local planners can use the map to determine whether extra care should be taken in new construction and whether it might be appropriate to retrofit some existing structures.

Last summer, a swarm of 1,600 tiny earthquakes – most unnoticed by the public -- occurred in the region. The temblors may have indicated magma moving deep beneath the Earth’s surface, according to

researchers at the Nevada Seismological Laboratory, Nevada Bureau of Mines and Geology, the California Institute of Technology, and the Harvard-Smithsonian Center for Astrophysics.

There have been several strong earthquakes in the greater Reno-Tahoe area in the past. Before seismic instruments were available, in 1860 and 1887, the region experienced two earthquakes in the magnitude 6.5 range. In 1950, a magnitude 5.6 earthquake was centered near Honey Lake northwest of Reno in Lassen County and in 1966, a magnitude 6 was centered north of Truckee. The 1966 quake damaged the dome of the Nevada state capitol in Carson City, cracked dams on the Truckee River and was felt as far away as San Francisco.

“People don’t necessarily relate the thought of earthquakes to the Reno-Tahoe area as readily as they do to Los Angeles or San Francisco,” CGS Chief Seismologist Michael Reichle said. “But it’s prudent for Californians and Nevadans alike in that area to be aware of the inevitability of future earthquakes and always be prepared.”

CGS, part of the California Department of Conservation, used soil information provided by Nevada officials and a seismic hazards model developed by the United States Geological Survey to produce the map. CGS previously produced a potential shaking map for California in cooperation with California Seismic Safety Commission and has extended the work into the greater Reno-Tahoe area with help from the Nevada Bureau of Mines and Geology as well as the Nevada Seismological Laboratory at the University of Nevada-Reno.

Copies of the map are available for $10 each from the California Geological Survey library at (916) 445-5716.

For more information about seismic activity in the Tahoe-Reno area and earthquake preparedness, click here.

In addition to studying and mapping earthquakes and other geologic phenomena, the Department of Conservation regulates oil, gas and geothermal wells; ensures reclamation of land used for mining; administers agricultural and open-space land conservation programs; and promotes beverage container recycling.

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