Towards characterizing the geometry and potential fault system connectivity at the southern termination of the Palos Verdes fault, offshore southern California

Dan Boyd, & Jayne M. Bormann

Published August 15, 2018, SCEC Contribution #8657, 2018 SCEC Annual Meeting Poster #249

The Palos Verdes fault (PVF) is a northwest-striking, strike-slip fault that cuts young marine and terrestrial sediments in the Los Angeles area from Santa Monica Bay in the north, across the Palos Verdes Peninsula, across the San Pedro Shelf and Slope to its southern terminus near Lasuen Knoll. The 95-km long fault 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. Slip rate estimates for the PVF range from ~1.5-3 mm/yr, and magnitude-length scaling relationships indicate the fault may be capable of producing a M7.3 event.

Despite posing significant hazard for coastal communities in Southern California, the geometry of the northern and southern ends of the PVF is poorly constrained. In recent years, several models of fault termination and connection have been proposed for the southern PVF. These models include: a through-going connection between the PVF and Coronado Bank fault to the southeast, PVF slip transferred to the Newport-Inglewood fault along faults northeast of Lasuen Knoll, the PVF as terminating in a horsetail-splay southwest of Lasuen Knoll, termination of the fault at Lasuen Knoll, or a left step between the PVF and Carlsbad Ridge fault at Lasuen Knoll.

Here, we focus on distinguishing between proposed models of PVF termination to reduce uncertainty due to unknown fault geometry in regional seismic models. We use a focused high-resolution multichannel seismic (MCS) reflection dataset collected over Lasuen Knoll in combination with legacy industry and USGS seismic reflection data to produce a detailed map of deformational structures at Lasuen Knoll. Preliminary mapping indicates that high relief at Lasuen Knoll is the result of southward-verging, east-west trending, compressional structures east of Palos Verdes fault. We find no evidence that Lasuen Knoll results from oblique compressional slip on a low-angle, eastward dipping segment of the PVF. Accepted models of PVF termination and kinematics should be consistent observations of east-west trending compression at Lasuen Knoll. Future work includes sequence stratigraphic interpretation to determine the relative timing of deformation on structures at Lasuen Knoll and an evaluation for potential rupture connectivity with neighboring fault systems.

Citation
Boyd, D., & Bormann, J. M. (2018, 08). Towards characterizing the geometry and potential fault system connectivity at the southern termination of the Palos Verdes fault, offshore southern California. Poster Presentation at 2018 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology