STRAIN PARTITIONING ACROSS THE EASTERN CALIFORNIA SHEAR ZONE

Although a significant amount of Pacific-North America plate motion is accommodated by the San Andreas Fault, roughly 30% of the relative plate motion is accommodated east of the Sierra Nevada-Great Valley block within the Eastern California Shear Zone (ECSZ) and Walker Lane Belt (WLB). Strain within the ECSZ is partitioned across three sub-parallel, dextral, oblique-slip fault systems; the Owen's Valley-Chalfant Valley, Panamint Valley-Hunter Mountain and Death Valley-Furnace Creek-Fish Lake Valley. North of the ECSZ, strain is partitioned between WLB (dextral transtension) and Central Nevada Seismic Belt (CNSB) (extension). The ECSZ and WLB are connected via the Mina Deflection, a right step-over in this dextral system.

We present a new GPS velocity field integrating six-year time series for sites across the WLB, CNSB and Mina Deflection with ten-year time series for sites across ECSZ. ECSZ site velocities relative to stable North America indicate dextral shear roughly parallel to the major faults, with rates decreasing from west to east. Whereas, site velocities to the north indicate extension across the CNSB, grading into dextral shear in the WLB. This new velocity field allows for a complete study of latitudinal changes in strain partitioning across this portion of Pacific-North America plate boundary. We investigate how strain is partitioned across this plate boundary by modeling several profiles normal to the strike of Pacific-North America plate motion. We utilize 2D viscoelastic coupling, finite element models to investigate earthquake cycle effects on the observed velocity field and how strain is partitioned on the different fault systems.