Scripps studies offer new picture of Lake Tahoe's earthquake...( For more than a decade scientists a...)

For more than a decade, scientists at Scripps Institution of Oceanography at UC San Diego have been unraveling the history of fault ruptures below the cobalt blue waters of Lake Tahoe one earthquake at a time. Two new studies by the Scripps research team offer a more comprehensive analysis of earthquake activity in the Lake Tahoe region, which suggest a magnitude-7 earthquake occurs every 2,000 to 3,000 years in the basin, and that the largest fault in the basin, West Tahoe, appears to have last ruptured between 4,100 and 4,500 years ago.

These studies, led by a team of Scripps researchers including Graham Kent, Neal Driscoll, Jeff Babcock and Alistair Harding, collected new data on earthquake history along three active faults in the region. These new data suggest that the most recent ruptures along the West Tahoe and Incline Village faults each produced nearly 4-meter-high offsets. The most recent event along the Incline Village Fault occurred about 575 years ago.

"These studies taken together show that the West Tahoe Fault is capable of a magnitude-7 earthquake similar to large earthquakes that have occurred on the nearby Genoa Fault but with the added danger of nearly 500 m of overlying water, which is capable of spawning a large tsunami wave," said Kent, a research geophysicist at Scripps.

Jeff Dingler, lead author on a paper in the April online issue of Geological Society of America Bulletin (GSA Bulletin) and former Scripps Oceanography graduate student, used a high-resolution seismic imaging technique, known as CHIRP, to supply a comprehensive view of faulting beneath the lake. Scripps' Neal Driscoll developed the new digital CHIRP profiler for this study, which provided an unprecedented picture of deformation within the sedimentary layers that blanket the floor of Lake Tahoe, laying the groundwork for more detailed fault studies that continue today.

In a complementary paper, published in the April issue
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