Abstract
The Buffalo Valley, Buena Vista Valley, and southern Shoshone faults are active range front normal faults that accommodate extension within the slowly deforming Basin and Range province in central Nevada. The faults are included as crustal sources in the 2023 update of the USGS National Hazard model, but with an absence of any earthquake recurrence data. Observations from lidar hillshades and field transects indicate the presence of progressively displaced alluvial fans along each fault. Here we present surficial geologic maps and vertical displacement estimates for the three faults. Additionally, we present descriptions of soil pits from displaced surfaces along the Buffalo Valley fault. Deformation along the Buena Vista and southern Shoshone faults is primarily concentrated along a singular fault strand. Vertical displacements from three alluvial fan surfaces along the Buena Vista fault include 1.5 m, 4 m, and 15 m. Along the southern Shoshone fault, alluvial surfaces are displaced 2.2 m and 10 m. Deformation along the Buffalo Valley fault is distributed across several parallel strands. Cumulative displacement across the oldest surface (three traces) is about 16 m and late Pleistocene fans are displaced between 1.75 and 4.2 m. A possible displacement of 0.75 m is recorded in a latest Pleistocene fan. Soils developed into late Pleistocene surfaces along the Buffalo Valley fault are characterized by thick (>1 m) textural B-horizons associated with stage III+ carbonate development suggesting the surfaces are greater than 100 ka. In progress ¹⁰Be surface exposure dates from surficial boulders and ¹⁰Be depth profile analyses from the soil pits will place age constraints on displaced deposits, and be used to estimate fault slip rates. These data will allow development of earthquake recurrence estimates for refinement of seismic hazard models, and for assessment of blind geothermal systems in the region.
Poster presentation.