DETERMINING THE TIMING AND OFFSET OF SECONDARY NORMAL FAULTS IN THE KIT FOX HILLS ADJACENT THE NORTHERN DEATH VALLEY FAULT ZONE

The Kit Fox Hills of Death Valley National Park California are composed of late Tertiary and Quaternary sediments uplifted by folding and faulting along the right-lateral Northern Death Valley Fault Zone (NDVFZ). Along the NDVFZ are arcuate normal faults that extend away from the fault at ~45 degree angle to the main fault zone, eventually assuming a strike that is parallel to the NDVFZ. The purpose of this paper is to determine the offset and age of these normal faults by the morphological degradation. Non-seismogenic secondary fault ruptures along fault zones represent a ground-rupture hazard to buildings near faults. Three fault scarp faces on secondary faults were examined and their profiles measured. All three faults offset Quaternary alluvial fan deposits. Two of the three scarps were found to have a maximum angle less than the angle of repose and thus amenable to the Bucknam and Anderson regression analysis for determining fault scarp age. Comparing the scarp angle and height to other scarps in the Basin and Range, scarp 1 has a height of 3.3 m and maximum slope of 20 degrees yielding an estimated age of 8-6 ka. The height of scarp 2 is 0.5 m with a maximum slope of 24 degrees producing an estimated age range of 1500-800 years. The third fault scarp has a 62 degree scarp face with a 1 m offset inferring (a) a relatively young scarp or (b) high-cohesion, carbonate-cemented soils. Other scarp studies in Death Valley have interpreted these high scarp angles as youthful scarps (500-600 years) or carbonate-cemented soils. Scarp 3 is the only scarp in the Kit Fox Hills with a free face and is not contiguous with other steep scarps, thus cemented soils is a likely interpretation. The carbonate cementation makes the determination of the age of scarp 3 undetermined. Examining scarp height/maximum slope relations suggests that these scarps formed due to at least two separate earthquakes and shows that ground rupture on secondary faults is a hazard that must be considered in areas near strike slip faults.