NORTHERN WALKER LANE SEISMIC HAZARDS AND STATE WATER PROJECT DAMS: UPPER FEATHER RIVER, CA

Positioned at the transition between Basin and Range extension and the north-west translation and uplift of the Sierra Nevada microplate, the northern Walker Lane shear zone is typically generalized as a system of four major left-stepping, en echelon, dextral fault zones. The faults of this system, listed east to west, are the Pyramid Lake, Warm Springs Valley, Honey Lake, and Mohawk Valley faults. Among and interconnected with these major faults are relatively minor normal and dextral faults. The contribution of these minor faults to the overall seismic hazard in the region is poorly constrained and understudied.

In this presentation we will follow up on the pre-meeting field trip where we explored potential seismic sources within the northern Walker Lane proximal to infrastructure managed by the California Department of Water Resources. Antelope Lake, Lake Davis, and Frenchman Lake, and their associated dams, are located between the Honey Lake and Mohawk Valley faults in the upper Feather River drainage. To assess the seismic hazard to these dams, we are conducting detailed Quaternary and bedrock geologic mapping complimented with recently acquired high-quality LiDAR data. This work will be used to document the presence, sense of displacement, activity, and slip rates (long-term and recent) of previously understudied faults that include the Indian Creek, Grizzly Valley, and Last Chance faults. The results of this ongoing work will aid in understanding regional tectonics and facilitate our assessment of seismic hazards at the headwaters of the State Water Project which supplies water throughout the state of California.