Geometry and Geomorphic Expression of Strike-Slip Faulting in the Central Walker Lane

Date: 4/24/2019

Time: 11:30 AM

Room: Vashon

Fault morphology and patterns revealed by high-resolution topography and imagery are indicative of dextral shear in the Carson, Smith, Mason, and Walker Lake basins. The shear is expressed either along discrete strike-slip faults, complex zones of numerous short faults, or obliquely on portions of previously mapped rangefront normal faults. Each of these zones is optimally oriented for the accommodation of geodetically observed northwest-directed dextral shear. Dextral slip rates on these faults remain unconstrained by quantitative geologic methods, though geodetic block modeled rates for each of these fault zones range from ~0.5-1.5 mm/yr, which seems reasonable based on their geomorphic expressions. Together the fault zones comprise a left-stepping en-echelon pattern that accommodates northwest-directed dextral faulting, extending from south of Hawthorne, NV to Sierraville, CA, and aligns with the previously documented strike-slip Fish Lake Valley and Mohawk Valley faults, to the southeast and northwest respectively. It is suggested that the series of faults may ultimately coalesce into a ~500-km-long through-going strike-slip fault connecting the entire Walker Lane. Where the Antelope, Smith, and Mason valley rangefront faults exhibit primarily normal displacement, vertical slip rates based on cosmogenic ages of faulted alluvial fans are reported. Quaternary deposits are mapped in each of these basins at a scale of 1:12,000. The distribution of scarp heights along the Antelope and Smith valley range-bounding faults are plotted to estimate the magnitude of displacement and recurrence intervals of the most recent and penultimate surface rupturing earthquakes, resulting in ~4-6 ka return times of ~M7 events, similar to that reported by previous trenching studies.

Presenting Author: Ian K. D. Pierce

Authors