Thursday, May 19, 2016

USA, California: Explanation for Geothermal Activity in the Walker Lane

Eastern California’s intense seismic and geothermal activity: Chicken or egg? (

A 13 May M=3.5 quake struck 30 mi (50 km) west of Death Valley at the northern tip of the Ash Hill fault. This quake is anything but an outlier: The ‘Walker Lane’ that extends between the eastern crest of the Sierra Nevada and into western Nevada was the site of the state’s third largest historical earthquake, in 1872, as well as some of the most vigorous seismic sequences in California since 1980. The Walker Lane accommodates 10-13 mm per year (0.5 in/yr) of right-lateral motion, about half of the San Andreas slip (Wesnousky, 2005), so by any measure is a major player in the Pacific-North American plate boundary.

A decade of seismicity reveals the strangely symmetrical distribution of earthquake clusters located beyond the ends of the 1872 Mw~7.6 earthquake. Both clusters enclose mixtures of hot springs, and extensional (‘normal’) faults and strike-slip faults, as well as sporadic eruptions in the past 12,000 or so years. Because of the hot springs, both have geothermal power plants. Several M>6 shocks struck in the 1980’s in the northern cluster, and several M~5 quakes struck in the 1990’s in the southern cluster.
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