SCEC Award Number 25262 View PDF
Proposal Category Collaborative Research Project (Multiple Investigators / Institutions)
Proposal Title Cracking the Klamaths: A not-so-rigid block linking the Walker Lane to the Mendocino Triple Junction
Investigator(s)
Name Organization
Michael Oskin University of California, Davis Kathleen Rodrigues Desert Research Institute
SCEC Milestones A3-5 SCEC Groups Geology, PBS, SDOT
Report Due Date 03/15/2026 Date Report Submitted 04/30/2026
Project Abstract
 We propose to use recently released and pending lidar datasets to search for and map active faults within the Klamath Mountains terrane of northern California. We will apply single-grain infrared stimulated luminescence (IRSL) dating to fault-bounded sedimentary deposits to quantify deformation rates on these faults. This information, synthesized with knowledge from faulting adjacent to the Klamath terrane, will be used to constrain the rate and style of active deformation accommodated directly east and northeast of the Mendocino Triple Junction (MTJ), where the San Andreas fault terminates. The Klamath terrane bridges between the northern termination of Walker Lane belt, to the east, which is characterized by dextral transtension, and the region of the MTJ, to the west, characterized by dextral transpression. The intellectual merit of our project is to characterize the non-rigid behavior of the Klamath mountains terrane to provide input to geodynamic models of the plate-boundary system and the MTJ in particular. The broader impacts of our project are (1) to define earthquake hazard in an area where no active faults are currently mapped. Though remote and sparsely populated, the region hosts critical water infrastructure including Shasta Dam, a keystone of the State Water Project that impounds the largest reservoir in California. (2) This project investigates the inboard effects of the transition from the San Andreas fault system to the Cascadia subduction zone, bridging between SCEC and CRESCENT. 3) This project involves a collaborator new to SCEC, Dr. Kathleen Rodrigues, from the Desert Research Institute (DRI).
Intellectual Merit We document a significant active north-south striking, east-dipping normal fault bounding Scott Valley, located within a basin surrounded by the highest topography
of the Klamath mountains. The fault extends for 47 km in a north-south direction, and the total fault length may be as much as 63 km. We determine a minimum dip-slip rate of 0.7 ± 0.2 mm/yr. This is a region of California located within the forearc of the southernmost Cascadia subduction zone, where there were no well documented active faults prior to this study. Geodesy shows that this region is under compression, opposite to the extension shown by active faulting.
Broader Impacts Though remote and sparsely populated, the Klamath Mountains region hosts critical water infrastructure including Shasta Dam, a keystone of the State Water Project that impounds the largest reservoir in California. The study area resides at the boundary between SCEC’s focus on California and the San Andreas fault system and CRESCENT’s focus on the Cascadia subduction zone, providing a bridge between these two earthquake centers. This project supports a UC Davis MS student thesis by Ryan Lynch and involves a collaborator new to SCEC, Dr. Kathleen Rodrigues, from the Desert Research Institute.
Project Participants Ryan Lynch, UC Davis MS student
Exemplary Figure Figure 3. Hillshaded lidar topographic map and surficial geologic map highlights scarp of the Scott Valley normal fault adjacent to Shackleford Creek. Plot shows a terrain profile across fault scarp with at least 12.5 meters of throw and 14.5 meters of dip-slip displacement. IRSL Age-dating of footwall deposits yields a minimum slip rate of 0.7 ± 0.2 mm/yr.
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