GEOLOGY: Death Valley in Slow Motion

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Science  01 Jun 2007:
Vol. 316, Issue 5829, pp. 1257a
DOI: 10.1126/science.316.5829.1257a

The San Andreas Fault is thought to mark the right-lateral slip between the North American and Pacific plates, but a large amount of the slip (~20 to 25) occurs on a set of faults farther inland, extending from Death Valley in eastern California up through western Nevada. These faults have produced some of the largest earthquakes within North America, comparable in size to temblors on the San Andreas itself, and this slip is responsible for the great depth of Death Valley. Today, the fault network near Death Valley is moving at about 12 mm/year, but whether this represents the long-term rate has been hard to determine. Frankel et al. measured cosmogenically produced radionuclides in boulders to date offsets in an alluvial fan in Death Valley. The long-term rate for the fault system for the past 70,000 years is indeed close to the current rate, whereas farther south, where several recent earthquakes have occurred, the current strain rate seems to be exceeding the long-term average. BH

J. Geophys. Res. 10.1029/2006JB004350 (2007).

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