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Evidence for Dextral-transpressional Quaternary-active Faults in the Northern Central Valley, California

Description: 

The northern Central Valley, California, has a long-lived history of faulting, but the locations and kinematics of active faults remains unknown. Regional tectonic models, largely based on geodetic data, suggest the region could accommodate transpression in a broad left-step as dextral shear is transferred westward from the Walker Lane across the northern Sierra Nevada microplate toward the southern Cascadia subduction zone. To better understand the locations and kinematics of the cryptic, low-rate deformation in the northern Central Valley, we integrated neotectonic mapping on historical aerial images and 1-m lidar-derived topography with 8 reprocessed seismic reflection profiles and InSAR. Neotectonic mapping of subtle fault-related features and apparently diverted channels shows evidence for at least 5 potentially active oblique-dextral faults that strike N50º-80ºE. Collectively, we call these faults the northern Sacramento Valley fault system, including the Dry Creek, South Cow Creek, Bear Creek, Battle Creek, and Red Bluff faults, from north to south. Juxtapositions and discontinuities of strata on the seismic reflection data are interpreted as ~20 subsurface faults that primarily offset Cretaceous and older strata, but at least 5 faults that extend upward into Pliocene (Tehama-Tuscan Fm) and Quaternary (Red Bluff Fm) strata. Several of the faults mapped in the subsurface data align with the neotectonic lineaments. A mismatch in stratal thickness across faults and broad zones of warped and folded strata, interspersed with multiple closely spaced faults with variable sense of slip, together suggests the faults may comprise transpressional flower structures, also consistent with the neotectonic mapping. Finally, discrete changes in northward interseismic strain accumulation that align with the mapped neotectonic features indicates these faults accommodate regional strain. Together, these data identify two new potentially active faults and support the presence of a distributed, low-rate dextral-transpressional N50º-80ºE-trending fault system at the northern end of the Central Valley.

Session: The Landscape Record of Earthquakes and Faulting [Poster]

Type: Poster

Date: 4/16/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Jessica

Student Presenter: No

Invited Presentation: 

Poster Number: 13

Authors