Late Quaternary deformation and seismic risk in the northern Sierra Nevada-Great Basin boundary zone near the Sweetwater Mountains, California and Nevada

Abstract

Remote-sensing, seismic and field studies indicate three major zones of Quaternary deformation near the Sweetwater Mountains. Holocene fault scarps are present in the Antelope, Little Antelope, Smith and Bridgeport Valleys, and in the Sonora Basin. Two other vaguely defined zones, between Carson and Antelope valleys, and from the Bridgeport Valley east to Bald Mountain, may represent Mio-Pliocene zones of faulting which more recently have acted as conjugate shears releasing stress between fault basins in the Western Great Basin between the Sierra Nevada and Walker Lane shear zone. The northern portion of the Sierra Nevada-Great Basin Boundary Zone is less active than the southern part in Owens Valley, as shown by lower slip rates, shorter fault lengths and lower levels of historical seismicity. Maximum Credible Earthquake magnitudes for the fault basins range from 6.3 to 7.2, with expected displacements of 3 meters or more.