Right‐lateral displacements and the Holocene slip rate associated with prehistoric earthquakes along the Southern Panamint Valley Fault Zone: Implications for southern Basin and Range tectonics and Coastal California deformation

Abstract

The N20°W‐trending Panamint Valley fault zone is linked to the N60°W‐trending Hunter Mountain strike‐slip fault and the Saline Valley fault system, which represents one of the three major fault systems accommodating active crustal extension in the southern Great Basin. A 25 km‐long zone of fault scarps along the southern Panamint valley fault zone is recognized as the surface rupture zone associated with the most recent prehistoric earthquake. The displacement associated with the most recent event, determined through six detailed topographic maps of offset features, is 3.2±0.5 m, and a number of larger offsets, in range of 6–7 m and 12 m, are also observed. If the larger displacements represent, respectively, two and three events, each of ∼3 m, then the fault zone appears to be associated with a characteristic earthquake, which we estimate from the length of the rupture zone and the displacement to be between (Ms) 6.5 and 7.2. The Holocene slip rate is 2.36±0.79 mm/yr, is determined from the displacement of two alluvial features whose maximum age is estimated from pluvial shorelines. Assuming a characteristic earthquake model, the recurrence interval is between 860 and 2360 years. The Holocene slip rate appears to be similar to the 4 million year slip rate of 2–2.7 mm/yr (determined from the Hunter Mountain fault), which we suggest reflects the relatively constant tectonics in this region over the last 4 million years. We further speculate that this supports the San Andreas discrepancy in that the Holocene slip rate of the San Andreas fault probably represents its very‐long term (several Ma) slip rate. The total slip vector of the southern Panamint Valley fault system is oriented toward ∼N35°W, making this a predominantly strike‐slip fault. In conjunction with the N60°W orientation of the Hunter mountain strike‐slip fault, we suggest that the displacement vector for the southern Great Basin is toward the NW, consistent with results from VLBI data, rather than WNW as determined by combining VLBI and geological data. This in turn suggests that the coastal California deformation component involves, respectively, less shortening and more strike‐slip displacement perpendicular and parallel to the San Andreas fault than is currently proposed.