Abstract

Maps showing Quaternary deposits and active fault traces, paleoseismic trenches, scarp diffusion analyses, and soil characteristics in displaced alluvial surfaces are combined with previous paleoseismic studies to examine the character of late Pleistocene earthquake recurrence and estimate the net extension rate across the interior of the Great Basin of the western United States at the latitude of ∼39°N. The study area includes faults bounding the Desatoya, Toiyabe, Monitor, Simpson Park, Toquima, Antelope, Fish Creek, Butte, Egan, and Schell Creek Ranges. The rate of earthquake recurrence is documented to be significantly less than observed within the Walker Lane–Central Nevada seismic belt and along the Wasatch, which respectively define the western and eastern boundaries of the interior of the Great Basin. Late Pleistocene extension across the interior of the Great Basin is calculated to equal ∼1 mm/yr across the 450 km transect and is consistent with rates defined by recent geodetic studies. The agreement in extension rate estimates over different time scales indicates that tectonic deformation in the Great Basin has been characterized by relatively slow and consistent extension through the late Pleistocene to the present. The internal deformation of the Great Basin and the pattern of strain release may reflect a broad transition zone from northwest-directed shear in the west to extension along the eastern edge of the Pacific–North American plate boundary.

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