Toward characterizing extension and Quaternary faulting on the Pleasant Valley fault, Central Nevada

Tabor J. Reedy, & Steven G. Wesnousky

Submitted August 15, 2017, SCEC Contribution #7803, 2017 SCEC Annual Meeting Poster #141

The Pleasant Valley fault is a 59 km long fault located approximately 30 km south of Winnemucca, Nevada. The fault system is the northernmost of a set of historical surface rupturing earthquakes that define the Central Nevada Seismic Belt (CNSB). The Pleasant Valley fault ruptured on October 2nd 1915 during a M7.2 earthquake. The surface ruptures and characteristics of earthquake recurrence along them were last the focus of study during the 1980’s. Here we use modern techniques to redocument and expand upon previous workers efforts to characterize the faulting on the Pleasant Valley fault. Several sites on Pleasant Valley fault preserve evidence of lateral slip and multiple late Pleistocene or Holocene earthquakes. Using high precision GPS, drone photography, and Structure from Motion software we create digital elevation models for the purpose of measuring normal and lateral offsets, Quaternary mapping, and scarp diffusion analysis. Preliminary horizontal and dip displacements from Golconda Canyon, Vesco Ranch, and North Miller Creek are used to define the rake of fault motion at each site and suggest an average slip direction oriented at 281o. Scarp diffusion modeling on profiles extracted from the digital elevation models of multiple event scarps at Siard Canyon are analyzed to suggest a penultimate event occurred 14.5 ky ago and created an ~4 m displacement. Additionally, we have excavated a 2m deep pit and collected sediment samples from a preserved multiple event surface at Siard Canyon. The sediment samples have been submitted for cosmogenic analysis and will provide another bound on the age of the penultimate earthquake and the fault slip rate. The cosmogenic age of the displaced fan at Siard Canyon may also contribute to the chronology of regional alluvial fan development and help place bounds on slip rates elsewhere along the Pleasant Valley fault and other faults in the region.

Key Words
Earthquake Geology, Neotectonics, Central Nevada Seismic Belt, Pleasant Valley

Citation
Reedy, T. J., & Wesnousky, S. G. (2017, 08). Toward characterizing extension and Quaternary faulting on the Pleasant Valley fault, Central Nevada. Poster Presentation at 2017 SCEC Annual Meeting.


Related Projects & Working Groups
Earthquake Geology