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Press Release 05-066
Scientists Develop New Profile for Lake Tahoe Earthquake Risk
Suite of Instruments Helps Researchers Calculate 3,000-Year Cycle for Large Quake
April 27, 2005
The deep, cobalt-blue waters of Lake Tahoe can mean different things to different people. For residents and tourists of the popular resort destination in the western United States, the lake's waters are a primary component of the area's serenity and beauty. For scientists, the lake's depth and rich color are an impediment to studying several important geological characteristics beneath the lake's basin.
Now, a team led by researchers at Scripps Institution of Oceanography at the University of California, San Diego, and funded by the National Science Foundation (NSF) has used a novel combination of scientific instruments to produce the first estimates for earthquake activity of several faults in the region.
The team's methods and results are described in the May issue of the journal Geology.
Lake Tahoe, which straddles the Calif.and Nev. border in the Sierra Nevada region, is one of the world's deepest freshwater lakes. At more than 1,600 feet deep, the lake covers 193 square miles over a fault basin prone to earthquakes and landslides.
The scientists' new 60,000-year record of fault movement, or slip rate, melds several emergent technologies and data sources. Scripps Institution's Graham Kent and his colleagues calculated the potential for a large, magnitude-7 earthquake occurring approximately every 3,000 years in the area.
Such an earthquake could produce tsunami waves some 6 to 30 feet high, research by Kent's colleagues at the University of Nevada, Reno, has shown.
Such an event would carry the potential for significant damage in the Lake Tahoe region, particularly through tsunami waves up to 30 feet in height that would emerge with little or no warning and slosh back and forth across the lake for an extended period of time, said Kent, a geophysicist at Scripps. "There are thousands of people on the beaches here in the summertime, so it's important to find out more about the history of such events in the area."
Ongoing and future research by the scientists will involve cataloging individual fault ruptures over the past 10,000 to 20,000 years to assess where each fault lies within its earthquake cycle.
"We are quantifying the recurrence intervals for Lake Tahoe to see how likely such an event might be in the future, especially in light of results suggesting that a large magnitude earthquake could occur approximately every 3,000 years," said Kent.
To get a clearer picture of Lake Tahoe, Kent and his colleagues used a device known as a CHIRP developed by Scripps Institution's Neal Driscoll, a coauthor on the new study. The digital CHIRP profiler beams acoustic signals at the lake floor to penetrate sediment layers and derive information about its seismic history. The researchers also used airborne laser technology and an acoustic mapping system to uncover several different aspects of lake characteristics. Finally, they extracted deep- and shallow-water sediment cores to analyze and date the lake's geologic history first-hand.
The research was also funded through grants from the Lawrence Livermore National Laboratory and the National Earthquake Hazard Reduction Program (United States Geological Survey).
-NSF-
Media Contacts
Cheryl L. Dybas, NSF (703) 292-7734 cdybas@nsf.gov
Mario Aguilera, Scripps Institution of Oceanography (858) 534-3624 maguilera@ucsd.edu
The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2009, its budget is $9.5 billion, which includes $3.0 billion provided through the American Recovery and Reinvestment Act. NSF funds reach all 50 states through grants to over 1,900 universities and institutions. Each year, NSF receives about 44,400 competitive requests for funding, and makes over 11,500 new funding awards. NSF also awards over $400 million in professional and service contracts yearly.
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