Imaging the southern trace of the Black Hills fault, Clark County, Nevada

The Black Hills fault (BHF) is a SE-dipping normal fault forming the northwestern structural boundary of the Eldorado basin, ∼20 km southeast of Las Vegas, Nevada (Langenheim and Schmidt, 1996). The fault offsets Holocene strata and is thus considered to be active (Fossett, 2005). Therefore, the BHF poses a significant seismic hazard to the greater Las Vegas area.;Fossett (2005) estimated that the BHF is capable of producing a M W 6.4 to 6.8 earthquake. However, this suggests a subsurface rupture length greater than the scarp length (Fossett, 2005). To test this hypothesis, remote sensing, geologic mapping, and high-resolution seismic reflection survey were utilized. The result is an interpretive geologic cross-section showing several SE-dipping normal faults on strike with the BHF. This implies that the BHF may be >6 km in length. In addition, several models are proposed to explain the anomalous orientation of the BHF relative to other normal faults in the area.