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Morphology, structure, and kinematics of the San Clemente and Catalina faults based on high-resolution marine geophysical data, southern California Inner Continental Borderland

July 10, 2020

Catalina Basin, located within the southern California Inner Continental Borderland (ICB), is traversed by two active submerged fault systems that are part of the broader North America-Pacific plate boundary: the San Clemente fault (along with a prominent splay, the Kimki fault) and the Catalina fault. Previous studies have suggested that the San Clemente fault (SCF) may be accommodating up to half of the approximately 8 mm/yr right-lateral slip distributed across the ICB between San Clemente Island and the mainland coast, and that the Catalina fault (CF) acts as a significant restraining bend in the larger transform system. Here, we provide new high-resolution geophysical constraints on the seabed morphology, deformation history, and kinematics of the active faults in and on the margins of Catalina Basin. We significantly revise SCF mapping and describe a discrete releasing bend that corresponds with lows in gravity and magnetic anomalies, as well as a connection between the SCF and the Santa Cruz fault to the north. Subsurface seismic-reflection data show evidence for a vertical SCF with significant lateral offsets, while the CF exhibits lesser cumulative deformation with a vertical component indicated by folding adjacent to the CF. Geodetic data are consistent with SCF right-lateral slip rates as high as ~3.6 mm/yr and transpressional convergence of <1.5 mm/yr accommodated along the CF. The Quaternary strands of the SCF and CF consistently cut across Miocene and Pliocene structures, suggesting generation of basin and ridge morphology in a previous tectonic environment that has been overprinted by Quaternary transpression. Some inherited crustal fabrics, especially thinned crust and localized, relatively hard crustal blocks, appear to have had a strong influence on the geometry of the main trace of the SCF, whereas inherited faults and other structures (e.g., the Catalina Ridge) appear to have minimal influence on the geometry of active faults in the ICB.