Paleoseismology of the Black Hills fault, southern Nevada, and implications for regional tectonics

Eric Fossett, University of Nevada, Las Vegas


The Black Hills fault (BHF) is a Holocene fault located in Eldorado Valley, ∼ 7 km from Boulder City, southern Nevada. The importance of this study is to determine the seismic hazards the BHF poses to Boulder City and the greater Las Vegas metropolitan area and to determine the mechanisms driving the young deformation in the Lake Mead region. The BHF is a multistranded fault that had five surface rupturing paleoearthquake events in the past ∼ 25 ka. Paleoseismic fault offsets indicate that the BHF is capable of generating a MW = 6.4--6.9 earthquake. Slip rates calculated for the BHF are 0.33--0.55 mm yr-1, which is significantly higher than the 0.01--0.1 mm yr-1 slip rates estimated for most of the faults in this region. The high slip rates on the BHF, and several other young faults in the Lake Mead tectonic domain (LMTD) may relate to deformation in the Death Valley area. Active dextral and transtensional faulting in the Death Valley region accommodates northwestward translation of the Sierra Nevada block, and thus creates strain accommodation space, which may drive extension to the east in the LMTD.