GEOMETRY AND NEOTECTONICS OF THE NORTHERN CALIFORNIA WASH FAULT, SOUTHERN NEVADA

The California Wash fault zone (CWFZ) is a N-striking, W-dipping normal fault bounding the western North Muddy Mountains that lies ~80 km NE of Las Vegas, NV. This study along the northern part of the fault defined fault geometry, documented the neotectonic history of the fault and assessed seismic hazards posed for the region.

Geologic map, scarp profile, and trench data suggest that the CWFZ is a young, multi-stranded fault zone. Geologic map data delineate up to 15 distinct strands and splays with as many as nine strands across strike. Most strands and splays dip W, but three dip E. Map and trench data show that the fault cuts units as young as Quaternary, possibly Holocene alluvial units and soils.

Trench and profile data suggest multiple slip events along the CWFZ. Scarp profile heights range from 1 to 23 m on the various strands. Three scarps >13 m high and cross-cutting relationships suggest multiple slip events.

Fault location, regional seismicity and the presence of scarps suggest the CWFZ poses seismic threat to I-15 and nearby communities. Calculations based on scarp height suggest earthquakes of M>7.0 may be possible along the fault.

Previous studies suggest different locations and geometries for the northern CWFZ. In one interpretation the fault has a relatively straight trace with a NNE-strike. In the alternative the fault bends from a NNE to a NW strike. Our map data are consistent with a relatively linear map geometry with a consistent NNE-strike.