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January 17, 2013
By Mike Wolterbeek
EarthScope, the world's largest earth-science program, has selected University of Nevada, Reno geophysicist and director of the Nevada Seismological Laboratory Graham Kent to lecture at several universities this year as part of their annual speaker series.
Kent will lecture in the National Science Foundation-funded EarthScope Speaker Series about underwater paleoseismology techniques he pioneered at Lake Tahoe with colleague Neal Driscoll of the Scripps Institution of Oceanography.
Kent and Driscoll's use of a digital, high-definition specialized acoustical radar method called CHIRP, and other new sonar technology, has allowed scientists to discover and define fault locations, slip-rates, earthquake recurrence intervals and other scientifically relevant data under lake and ocean bottoms. Kent will introduce their newest device, developed with acoustic equipment designers at EdgeTech, which will allow high-resolution images of sub-strata as deep as 300 to 400 meters below a body of water.
"We do things a little differently underwater than on land," Kent said. "We began at Tahoe about 12 years ago using cutting edge technology with a new application - digital CHIRP sonar to map beneath bodies of water to see, at that time, the offset layers of sediment down to about 50 meters. This capability has in turn allowed the field of underwater paleoseismology to blossom. (Think sonar instead of digging a ditch with a backhoe.)
"We've stayed at the leading edge of this technology and have the only University-based digital system that can perform this type of research. It's like a time machine. The farther down in depth we can see, the farther back in time we can see—and without sacrificing quality. This gives unbelievably high-resolution images of the sub-surface."
Kent and his team have done innovative work throughout the western United States, such as discovering and quantifying ancient tsunamis at Lake Tahoe that will occur again. They've explored beneath the Salton Sea, discovering that flooding into ancient Lake Cahuilla triggered earthquakes. These same faults will rupture again and may once again set off the notorious San Andreas Fault in southern California. In addition, while studying the West Tahoe fault beneath Fallen Leaf Lake, they explored ancient shorelines ringed by a standing forest of trees submerged under 110 feet of water from which they have compiled the most accurate record of the last megadrought in the Sierra Nevada range. This particular megadrought lasted approximately 200 years.
Kent's first stop on the EarthScope Speaker Series begins today at Oregon State University. EarthScope is a program of the National Science Foundation that involves collaboration among scientists, educators, policy makers and the public to learn about and utilize exciting scientific discoveries as they are being made. Other universities in the tour include University of Utah, Colorado State University, Vanderbilt and University of Wisconsin at Madison.
Kent's lecture is titled "Development of Underwater Paleoseismic Techniques: An Application to Transtensional Environments Along the Western U.S. Plate Boundary."