Preliminary paleoseismic observations of the Ione Valley Fault, Basin and Range Province, central Nevada

James C. McNeil, & Rich D. Koehler

Published August 16, 2021, SCEC Contribution #11574, 2021 SCEC Annual Meeting Poster #079

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. We conducted Quaternary geologic mapping along the Ione Valley fault using Google Earth satellite imagery, SRTM 1 arc-second imagery, and field reconnaissance to develop information to guide more detailed investigation along the fault. Additionally, we developed detailed DEM’s derived from drone surveys at select locations. Here we present preliminary mapping observations and initial interpretations of the DEM models. The observations indicate the presence of faulted alluvial surfaces of different ages and with varying scarp heights, supporting a history of progressive active deformation. In the south, the fault is expressed as a series of left and right stepping strands that displace relatively old alluvial surfaces. The scarps are up to 9 m high and have rounded crests, lack a free face, and have a smoothed debris slope and wash slope with well-developed vegetation. Further north, the fault is expressed as a prominent rangefront trace and up to 5 m high piedmont scarps across intermediate alluvial fans. Scarps across young alluvial fans were not observed suggesting that the most recent event predates the Holocene. Based on these preliminary observations, we plan to estimate the age of the faulted surfaces using cosmogenic depth profiles to place constrains on the fault’s late Pleistocene slip rate and recurrence. 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.

Key Words
Paleoseismology, Quaternary, Pleistocene, Holocene, Fault, Scarp, Basin and Range, Walker Lane, slip rate

Citation
McNeil, J. C., & Koehler, R. D. (2021, 08). Preliminary paleoseismic observations of the Ione Valley Fault, Basin and Range Province, central Nevada. Poster Presentation at 2021 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology