Termination of the Palos Verdes Fault at Lasuen Knoll: Evaluating Models of Geometry, Kinematics and Potential Connectivity

Daniel Boyd, & Jayne M. Bormann

Published August 15, 2019, SCEC Contribution #9868, 2019 SCEC Annual Meeting Poster #116

The Palos Verdes fault (PVF) is an active component of the Inner California Borderlands offshore strike-slip fault system that collectively accommodates ~6-8 mm/yr of Pacific-North American plate boundary shear. The PVF extends 95 km from Santa Monica Bay in the north, across the Palos Verdes Peninsula, through the San Pedro Shelf and Slope to Lasuen Knoll (LK). Slip rate estimates for the PVF range from ~1.5-3 mm/yr, and magnitude-length scaling relationships indicate the fault could generate a M7.3 event. Despite posing a significant hazard for coastal communities in Southern California, the geometry at both ends of the PVF remains poorly constrained. Several models have been proposed to explain the southern fault termination and the potential for connectivity with neighboring faults. These models include: 1) a throughgoing linkage between the PVF and Coronado Bank fault (CBF), 2) slip transfer between the PVF and the Newport-Inglewood fault (NIF) along faults northeast of LK, 3) PVF termination in a horsetail-splay southwest of the knoll, and 4) PVF termination at LK, with a left step between the PVF and Carlsbad Ridge fault (CRF).

To reduce uncertainty in fault geometry and distinguish between proposed fault termination models, we use a sequence stratigraphic approach to interpret high-resolution and legacy industry 2D seismic reflection data to map deformational structures at LK and constrain the relative timing of activity of these structures. We observe that the southward growth of E-W trending compressional folding to the east of the PVF corresponds with high relief at LK, and this folding is bound to the south by a deformation front that extends eastward from a ~1 km restraining bend in the PVF. This folding matches the predicted style of deformation found in the contractional quadrant around a right-lateral fault termination. Similarly, an extensional horsetail-splay damage zone lies immediately south of the termination of the northwest striking fault, in the dilational quadrant. We find no evidence for kinematic or temporal linkage between the CBF and PVF, supporting mapping by Conrad et al., (2010, 2018) and Ryan et al., (2009, 2012). The discontinuous faults east of LK are on strike with structures in the San Mateo trend that may transfer slip to the NIF system; however, the role of these structures in slip-transfer is unknown.

Boyd, D., & Bormann, J. M. (2019, 08). Termination of the Palos Verdes Fault at Lasuen Knoll: Evaluating Models of Geometry, Kinematics and Potential Connectivity. Poster Presentation at 2019 SCEC Annual Meeting.

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