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Finding Faults:
MSU Researchers Study the Shakes


By Evelyn Boswell

Residence damaged (right) after two earthquakes hit Helena in 1935. (Photo from the Montana Historical Society.)
When an earthquake jostled Montana State University-Bozeman last summer, it was nothing new to Joseph Fedock, vice provost for academic affairs.

Fedock is an earthquake engineer who figures he survived 11 good-sized earthquakes before moving to Bozeman in 1990. Clearly, he knew what was happening when his chair started rocking in Montana Hall. "It was very definitely an earthquake," Fedock said of the Aug. 20 quake that brought back all the instincts he'd honed during his California years. (Don't bolt from a building while it's shaking, for example). Admittedly, Montana's 5.3 earthquake didn't measure up to the 1989 Loma Prieta quake that hit the San Francisco Bay area with Fedock 15 miles from the epicenter. It couldn't touch last year's worldwide earthquakes as far as devastation. But Montana's quake did draw attention to what Fedock and a handful of MSU researchers have been saying all along -- that California isn't the only state that gets the shakes. Montana, in fact, is the fourth most seismically active state in the nation. "All of the western United States is earthquake country," said David Lageson, professor of structural geology. "It's just one seismic belt after another." Montana's earthquake also spotlighted the seismic research and public outreach that's coming out of MSU-Bozeman these days. The earth sciences, architecture and civil engineering departments all have researchers addressing questions related to earthquakes. The researchers and Fedock are also trying to convince Montanans that earthquakes can really happen here. "I'm kind of amazed at the lack of understanding or just even acceptance of the fact that this is earthquake country," commented Lageson, a kind of prophet in his own land. "Most Montanans just don't consider this to be a seismically active region. That always amazes me."

Understanding faults

Lageson's research is focused on understanding the development of the Rocky Mountains and the western United States. He is currently concentrating on southwest Montana and is especially interested in the Paradise Valley south of Livingston and the Centennial Mountains on the Idaho border. He is studying the Bridger Range, as well. "There are a lot of indications that suggest the Bridger Range is geologically young, but we have very poor scarp records for that range," Lageson said. A fault scarp is an obvious place where the surface of the earth has been broken by a fault during an earthquake. In the Greater Yellowstone area, a fault scarp would be a very discrete step upward. It might be one to several meters high. Lageson's goal is to understand the structural controls on contemporary and ancient faults. He wants to know, for example, why faults exist where they do and the effect of past earthquakes on the region's faults. To find out, Lageson spends much of his time "doing field work, constructing geological maps of the area, looking at recent fault scarps, measuring scarps and looking at other landscapes for active uplift." Lageson works in the field with Cal Ruleman, an MSU graduate student. His collaborator on contemporary earthquakes is Mike Stickney, director of the Earthquake Studies Office at Montana Tech. Lageson's collaborator for paleoseismology, or quakes older than recorded history, is Ken Pierce of the new U.S. Geological Survey's Northern Rocky Mountain Research Center at MSU. He and Pierce have found a definite lack of earthquake activity in the Paradise Valley during the 20th century, Lageson said. Despite evidence that major earthquakes occurred there in the last 10,000 years, the valley appears to have a "seismic gap," or locked fault. "It sticks for a long time and then slips," Lageson observed. "It could be a gap. It could be locked because that fault system is at an odd angle."
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