PALEOSEISMICITY OF THE CALIFORNIA WASH FAULT, SOUTHERN NEVADA

The California Wash fault (CWF) is a NNE-striking down-to-the-west normal fault along the western North Muddy and Muddy mountains, southern Nevada. This active fault offsets Quaternary strata and has scarps as high as 10.3 m. We used fault geometry, paleoseismicity, and geomorphic history to assess the seismic hazard posed by the CWF. The central CWF is geometrically simple with just 1 or 2 strands across strike. However, near both fault ends it has as many as 7-10 strands across strike. A right step over in the scarp along the central CWF suggests fault segmentation and linkage occurred. Two wash cuts through the CWF scarp each expose three colluvial wedges up to 1.06 m high. One major and three minor fault strands are exposed in the southern dissection and 7 (1 major, 6 minor) are exposed in the wall of the northern wash. A radiocarbon date of 16,105 +/- 355 Cal BP from footwall sediments in the northern dissection suggests that the three colluvial wedge-forming seismic events occurred since then. Scarp diffusion modeling along the central scarp yielded dates of 11.5 and 5.8 ka. These ages and variations in scarp height along strike combined suggest the age of the MRE varies along strike, and behavioral (earthquake) segments may exist along the CWF. Surface rupture lengths, colluvial wedge heights, and scarp heights indicate the CWF is capable of earthquakes of M 5.9-7.0. An earthquake of this magnitude along the CWF could impact a power plant, I-15, small towns, and the Las Vegas metropolitan area.