The degree to which fault loading and strain release rates are constant (or non-constant) in time and space is one of the most fundamental, unresolved issues in modern geodynamics. Comparisons of short-term geodetic data with very long-term (million year) global plate motion data indicate that, along most plate boundaries, strain storage and release are relatively continuous over a large temporal range. Recent comparisons of geodetic and geologic rate data across the Mojave section of the eastern California shear zone however, point to the occurrence of a pronounced strain transient. These observations raise several fundamentally important questions about how strain accumulates and is released along major plate boundary fault systems. A team of scientists from the University of Southern California, University of Cincinnati, and University of California at Berkeley seeks to understand the spatial and temporal constancy of strain accumulation and release in the northern half of the eastern California shear zone. Specifically, the work will focus on the Death Valley-Fish Lake Valley fault zone, the largest fault system in the region, extending over 300 km from the Garlock fault northward into southwest Nevada. Fault slip rates are being determined at a variety of geologic time scales (1,000 - 100,000 years) along the length of the fault system by dating offset alluvial landforms with cosmogenic nuclide and optically stimulated luminescence geochronology. Deformed geomorphic features are identified, mapped, and restored based on airborne laser swath mapping digital topographic data, acquired in a two-kilometer-wide swath along the fault to allow the research team to determine the geomorphic context of the fault zone and to capture any secondary fault strands or off-fault deformation. Comparison of geologic slip rates determined from the Death Valley-Fish Lake Valley fault zone with short-term geodetic data (decadal) and geologic slip rates from other faults in the region will allow the team to evaluate if the transient strain accumulation observed in the Mojave segment of the eastern California shear zone extends northward as a fundamental feature of the Pacific-North America plate boundary or is alternatively, tied to the zone of structural complexity associated with the Big Bend of the San Andreas fault. The research team will work closely with the U.S. National Park Service in Death Valley National Park to disseminate results of this project to park visitors.
