Active faulting in the North Valleys region of Reno, Nevada: A distributed zone within the northern Walker Lane

摘要

At the latitude of Reno, Nevada, USA, similar to 15-25% of the Pacific/North American plate boundary strain is accommodated east of the Sierra Nevada through a combination of normal oblique (dextral) slip along the eastern Sierra Nevada range front and dextral slip along faults in the northern Walker Lane. The North Valleys region sits within the northern Walker Lane directly east of the Sierra range front and is characterized by a series of small north striking basins bound by Quaternary active faults that accommodate dextral oblique extension. Geodetic studies of the North Valleys estimate that the faults collectively accommodate 0.9-1.7 mm/y of extension and 0.3 mm/y of dextral slip; however, few Quaternary geologic/paleoseismic studies have been conducted.In this paper, geologic observations on the tectonic geomorphic expression and relative activity of faults within and bounding the North Valleys are described, including the Last Chance, Petersen Mountain, Fred's Mountain, and Spanish Springs Valley fault zones, and several un-named faults in Lemmon and Hungry valleys. Geologic observations from the interpretation of lidar-derived hillshade images, aerial photographs, satellite imagery, and field reconnaissance indicate that the faults all exhibit evidence of late Quaternary deformation, including offset alluvial fan deposits and abrupt range-front escarpments. The results indicate that the faults of the North Valleys are capable seismic sources characterized by extension rates on the order of hundredths to tenths of millimeters per year. The faults act to transfer slip from the Sierra Nevada range front to the northeastern Walker Lane by accommodating dextral oblique extension consistent with pull-apart basin kinematics within a simple shear right-lateral system. Published by Elsevier B.V.