Collaborative Research: Testing Tectonic Geodesy from Fault Slip Rates Across the Eastern California Shear Zone

University Of North Carolina At Chapel Hill, Chapel Hill NC

Investigators

Abstract

The Eastern California Shear zone is an intriguing example of a plate boundary fault system where the known rates of faulting may not add up to the geodetic rate of strain accumulation. This research tests the hypothesis that geologic and geodetic strain rates must somehow agree across the Eastern California Shear zone by gathering new long-term slip rate data from a well-defined, well-exposed, and tectonically simple transect of active faulting across the central Mojave Desert. Field geomorphic and geologic mapping, augmented by targeted acquisition of high-resolution airborne laser swath mapping altimetry data, will document offset Plio-Quaternary lava flows and alluvial fans across each of six right-lateral strike-slip faults. Selected offset markers will be dated with 40Ar/39Ar, cosmogenic 10Be or cosmogenic 3He to measure crustal deformation rates at 10^5 to 10^6 year time scales that average several earthquake cycles. If the geology does account for the geodetic strain rate through significant slip rates on one or more faults, the predictive capability of tectonic geodesy is demonstrated. Alternatively, if the long-term geologic strain rate is significantly slower than the geodetic rate, as seems to be supported by existing paleoseismic data, then a system-wide transient loading process must be responsible for the high present-day strain accumulation across the Eastern California Shear zone.