Abstract

Seven trenches in eastern California across the Owens Valley fault near Lone Pine expose two episodes of faulting since early Holocene time in the form of ∼1 m throw in lacustrine beds with liquefaction that were buried and then faulted again ∼1 m by the M 7.5 to 7.75 A.D. 1872 Owens Valley earthquake. Geomorphic maps, applications of sequence stratigraphy, and analyses of radiocarbon from charcoal and tufa deposits indicate that the paleoearthquake, the penultimate event here, occurred between 10,200 ± 200 and 8800 ± 200 cal yr B.P. The cumulative vertical displacement from these last two earthquakes in three trenches averages 2.4 ± 0.3 m (2σ), and the penultimate event has slightly larger displacements. A synthesis of available data indicates that the antepenultimate event was probably as large and occurred between ca. 24,000 and 14,000 cal yr B.P. (2σ). Thus, the two interseismic intervals between the last three surface-faulting earthquakes on the southern Owens Valley fault are each ∼10,000 yr. This ∼25,000-year record indicates that the “two-event” normal-oblique slip rate on the Owens Valley fault near Lone Pine is 1.0 ± 0.5 m/k.y. This result is similar to that of several previous geological studies here, yet it is still slower than slip rates on the northern Owens Valley fault and several factors slower than contemporary geodetic measurements. This study attempts to account for different dating methods and interpretational uncertainties, to acknowledge how little is known about the slip history of the Owens Valley fault and adjacent faults, and to consider the role of segmentation, as well as splay and distributed faulting, in comparisons of displacement data among different sites along the entire ∼100 ± 10 km length of the Owens Valley fault.

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