PRELIMINARY PALEOSEISMIC OBSERVATIONS OF THE IONE VALLEY FAULT, BASIN AND RANGE PROVINCE, CENTRAL NEVADA

The Ione Valley fault is a north-northeast striking, range-bounding, dip-slip fault that bounds the western margin of the Shoshone Range in west-central Nevada. The fault sits directly east of the Mina deflection, a major right step in the NW structural grain of the central Walker Lane that accommodates ~8 mm/yr of the geodetically measured Pacific/North America relative shear. At this latitude, part of the regional strain is transferred to faults of the western Basin and Range as evidenced by historical earthquakes within the Central Nevada Seismic Belt (CNSB) that are associated with both normal and dextral displacement. The Ione Valley fault is subparallel, and southeast of the CNSB, and is one of a series of other parallel faults that project to and terminate against the Walker Lane. The relative role of these faults in accommodating regional shear is an area of ongoing research and the earthquake history, faulting behavior, and slip rate for the Ione Valley fault is poorly characterized. Thus, we conducted Quaternary geologic mapping along the fault using Google Earth satellite imagery and SRTM 1 arc-second imagery to develop information to guide more detailed investigation of the fault. Preliminary observations indicate the presence of faulted alluvial surfaces of different ages and with varying scarp heights supporting a history of progressively active deformation and surface-rupturing paleo-earthquakes. In the south, the fault is expressed as a series of left and right stepping strands that displace relatively old alluvial surfaces. Further north, the fault is expressed as a prominent rangefront trace and piedmont scarps across intermediate alluvial fans. Based on these preliminary observations, we plan to conduct additional neoteconic studies along the Ione Valley fault to better characterize its paleoseismic history and develop earthquake timing and slip rate data. These data are important for regional seismic hazards models and may potentially contribute towards a better understanding of strain partitioning along the Basin and Range/Walker Lane transition zone.