UC Davis

The Klamath Mountains province (KMP) of northern California and southern Oregon has traditionally been characterized as a rigid crustal block due to a lack of formally recognized active faults. However, the identification of active faults is hindered by the elevated, eroding, and densely forested character of the KMP, and assumptions of rigidity are inconsistent with the region’s likely weak rheology and geodetic evidence of active transgressional deformation. I utilize recently released high-resolution lidar data to identify three active normal faults and one active dextral strike-slip fault in the KMP. I focus on the 47-km-long Scott Valley normal fault to provide the first geologic constraint on the rate of active deformation in the KMP. Fault scarp displacement analysis and Infrared Stimulated Luminescence dating indicate a minimum mean dip-slip rate of 0.7 ± 0.2 mm/yr since 21.2 ± 4.4 ka for the Scott Valley normal fault. I expect that ruptures on active normal faults in the KMP coincide with a stress field reversal induced by a CSZ megathrust event. Finally, I interpret north-south striking normal faults in the KMP as evidence of active east-west extensional deformation, which I attribute to southern Cascadia slab rollback and/or subcretion.