Nov. 16, 2007 -- A sleepy, San Andreas-like earthquake fault near Las Vegas could someday wake up, say geophysicists.
The Stateline Fault comes within 30 miles of Las Vegas and the proposed high-level nuclear waste repository at Yucca Mountain, north of Vegas. It also runs right through backyards in the fast-growing community of Pahrump, Nev., to the west.
"Big faults, in between earthquakes, are generally very quiet," said Caltech geophysicist Brian Wernicke. He is a coauthor of a report on the Stateline Fault which appears in the current issue of the Geological Society of America Bulletin.
New evidence that the fault can move more than previously reported includes some debris from a small volcano along the fault which has been shifted more than 20 miles away from the volcano over the last 13 million years. This suggests that the real rate of San Andreas-like lateral "strike-slip" movement on the Stateline Fault could be twice the earlier estimates.
"The strike-slip story is just emerging," Wernicke told Discovery News. Part of the reason for the lack of previous understanding is that the fault wasn't even identified as one long feature until the first Landsat satellite images were taken from space in the early 1970s, said Wernicke.
Since then, the populations of Las Vegas and Pahrump have exploded.
"Ninety-nine percent of the population of Pahrump has no idea that they're right on top of the fault," said geophysicist Terry Pavlis at the University of Texas in El Paso. "This is close enough (to Vegas) that you'd get a pretty good shaking if this thing were to go."
The historic measurements of slip along the Stateline Fault suggested the fault was slipping laterally at a gentle rate of a millimeter or so per year. It was also judged to be more of a vertically-moving fault, like those throughout the Great Basin which built a fleet of mountain ranges and basins extending from eastern California through Nevada and into Utah.
As a strike-slip fault, however, it could be part of a growing set of north-south running faults in eastern California and western Nevada that some geologists suspect are gradually taking over the San Andreas' role as the major boundary between the North American and Pacific tectonic plates.
More data on the current movements along the faults are possible because of a recently installed GPS survey system for the Yucca Mountain Project, said Wernicke. However, funding for analyzing data form the GPS system was recently cut by the Department of Energy, he said.
Related Links:
Larry O'Hanlon's blog: Earth Impacts
Howstuffworks.com: Earthquakes
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