Offset Quaternary deposits, measurements of fault scarps, and the excavation of two trenches along the eastern Sierra Nevada range front provide information on the rate and style of active faulting in Antelope Valley, California, and Reno, Nevada. Structural, stratigraphic, and pedogenic relations exposed in a trench in Antelope Valley (forumla latitude) record two Holocene surface-rupturing earthquakes. Radiocarbon dates place the most recent and penultimate events at about 1350 calibrated years before present (cal B.P.) and older than about 6250 cal B.P., respectively. An approximate fault-slip rate of ∼0.7 mm/yr is calculated by dividing the 3.6-m offset that occurred in the most recent event by the time between the two radiocarbon ages (∼5000 years). A second trench excavated across the Carson Range frontal fault in Reno, Nevada (forumla latitude) revealed a sharp, planar, low-angle failure surface dipping 33° E, lending to the possibility that the active normal fault is characterized by a dip much lower than expected from standard frictional considerations.

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