Integrated Geologic and Geodetic Study of Strain Accumulation and Release in the Northern Walker Lane

Board Of Regents, Nshe, Obo University Of Nevada, Reno, Reno NV

Investigators

Abstract

Pacific-North American right-lateral relative plate motion at the latitude of the San Andreas fault system is approximately 50 mm/yr. Up to one fourth of that motion is accommodated by displacements on faults east of the San Andreas fault system within the Eastern California shear zone and Walker Lane system located in the western Basin and Range province, eastern California and western Nevada. Unlike the San Andreas system, the relative immaturity and complexity of the northern Walker Lane fault system makes the comparison between geodetic and geologic rates difficult. Current data indicate that there is a systematic difference between rates of moment release (obtained from geologic observations of offset markers and paleoseismic investigations), and rates of strain energy accumulation (estimated from geodetic measurement of surface shape change) in the western Basin and Range. The current lack of understanding of this discrepancy may lie in the incompleteness of data on strain release (as seen through structure, physiography, and the spatial and temporal distribution of earthquakes) and the resolution of slip rates based on strain accumulation (as seen by geodesy) in a complex intra-continental setting. This project is an integrated neotectonic and geodetic analysis of the northern Walker Lane in the area between Walker Lake and Lake Tahoe, a region for which the neotectonics data are very minimal. In order to evaluate the difference between budgets of strain accumulation and release a University of Nevada at Reno research team will obtain the most complete measurements to date of these two manifestations of the earthquake cycle in an intra-continental setting. The project uses geodetic data from existing or soon-to-be installed networks (BARGEN, MAGNET, NEARNET, and the EarthScope Plate Boundary Observatory) that will be supplemented with a new geodetic network that uses a semi-continuous observation strategy to obtain roughly three times as many high precision rates as are currently available in the study area. A variety of neotectonic approaches will be used to study the faults bounding the Smith, Mason, Antelope and Bridgeport Valleys and long the Wakuska and Carson lineaments. The scale of the investigation will achieve a maximum in overlap between the strengths of the two disciplines, small enough to obtain a geologic record that is representative, and large enough to resolve variations in the geodetic strain field that can be related to crustal fault patterns. This work is in concert with the goals of EarthScope. Specifically, a complete understanding of the kinematics and mechanics of any plate boundary requires measurements of the rate, style, and evolution of deformation across the entirety of the boundary through geologic time. Results from this study will aid in understanding earthquake hazards in this seismically active region.