Lidar-Based Evaluation of Faulting in the Northern Walker Lane, Upper Feather River Watershed, Plumas County, California

Date: 4/24/2019

Time: 06:00 PM

Room: Fifth Avenue

To investigate Quaternary deformation across the northern Walker Lane, a zone of right-lateral shear between the Sierra Nevada and the Basin and Range in Plumas County, we analyzed high-resolution (10 points per square meter) airborne LiDAR data covering 1,008 square kilometers acquired for the California Department of Water Resources. Comparison of high-resolution topography developed from LiDAR data with regional geologic mapping documents the presence of geomorphic features coincident with previously mapped late Quaternary faults including the Indian Creek, Grizzly Valley, and Last Chance faults. In addition, mapped potentially tectonic-related features coincide with previously mapped bedrock faults and across areas of undifferentiated bedrock, providing information on possible locations of previously unrecognized late Quaternary faulting. Subsequent field mapping verified tectonically deformed geomorphic features including linear scarps in alluvial surfaces, elongated depressions aligned with adjacent linear escarpments, truncated bedrock spurs, closed depressions, linear swales, right-lateral deflections of creeks and river courses, and shutter ridges, as well as springs and linear seeps consistent with oblique strike-slip faulting. The discontinuous nature of many of the observed potential fault traces are consistent with incipient faulting undergoing simple shear deformation between the Honey Lake fault (HLF) in the east and Mohawk Valley fault (MWF) in the west. The NW-SE orientation of the MWF and HLF is consistent with regional geodetic plate boundary deformation measurements. The fragmented nature and orientation of the mapped faults is consistent with secondary faulting manifested as synthetic riedel shears and normal faults. This study complements on-going investigations by DWR to assess the impact of seismic hazards on State Water Project infrastructure.

Presenting Author: Christopher Hitchcock

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