Complete fault kinematics of the creeping faults in central California - San Andreas Fault and Calaveras Fault

Li-Chieh J. Lin, & Gareth J. Funning

Submitted September 7, 2025, SCEC Contribution #14808, 2025 SCEC Annual Meeting Poster #TBD

The central San Andreas Fault and the Calaveras Fault are known for their relatively fast creep rates, ranging from about 1 to 3 cm/yr depending on the location. Despite these rapid creep rates, some fault segments still hold significant slip deficits, suggesting the possibility of potential large earthquakes. Understanding the complete fault kinematics is crucial, as it reveals how these faults interact with long-term tectonic loading and the resulting slip vectors. Previous studies have primarily focused on quantifying the creep rates, often assuming pure strike-slip motion and attributing all deformation to fault movement. However, these assumptions may not always hold, as fault slip is a complex process and surface deformation can also be induced by non-tectonic sources.

In this study, we jointly analyzed spaceborne Sentinel-1 and airborne UAVSAR data to construct the long-term 3D surface deformation field. Using UAVSAR as a strong constraint on the north–south motion, our results reveal strong fault creep signals in the fault-parallel direction, fault compression in the fault-perpendicular direction, and relatively subtle vertical offsets across the faults. Although the vertical offset is roughly an order of magnitude smaller than the fault-parallel motion, its non-zero value indicates that both the San Andreas and Calaveras faults are slipping obliquely. The observed secular compression in the fault-perpendicular direction is consistent with the current topography and the regional stress field. We also find that parts of the San Andreas Fault’s creep are partitioned onto the Calaveras Fault, together totaling about 2 cm/yr of creep and leaving a slip deficit of roughly 1 cm/yr. These results improve our understanding of the complete fault kinematics and provide better constraints for future earthquake occurrence estimates.

Key Words
InSAR, Creep rate, Fault kinematics, 3D surface velocity field

Citation
Lin, L. J., & Funning, G. J. (2025, 09). Complete fault kinematics of the creeping faults in central California - San Andreas Fault and Calaveras Fault. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy