Abstract

Seismicity in the Excelsior Mountains area appears to have been an order of magnitude higher for at least several decades than that which preceded great earthquakes in central Nevada in 1915 and 1954. A high degree of crustal fracturing is indicated for this area by complex geology and by a scattered distribution of epicenters. A composite fault-plane solution is similar to those for large shocks at Fairview Peak and Rainbow Mountain in 1954, which shows that the same regional stress field is acting to produce earthquakes in both areas. The slope of the recurrence curve, or b value, is higher than average for the Nevada region. Crustal strains recorded at Mina indicate that periods of strain build-up alternate with periods of strain release. Comparison of these characteristics with results of laboratory experiments and observations in other regions suggests that the area is one in which a moderate level of tectonic stress combined with a high degree of crustal fracturing leads to strain release by a continuing series of small-to-moderate earthquakes and fault creep. If so, the magnitude of 6¼ for the 1934 Excelsior Mountains earthquake may represent a maximum magnitude for this area.

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