Analysis of Fault Interaction and Deformation along the Newport-Inglewood Rose Canyon and San Onofre Trend Fault Systems Using High-Resolution 3D P-Cable Seismic Reflection Data

Ocean Sciences Meeting (OSM), 16-21 February 2020, San Diego, CA, USA

Off the coast of southern California and Baja, the Inner California Borderlands (ICB) is a highly deformed region recording transtension and transpression. Geodetic and geologic observations indicate that approximately 6-8 mm/yr of Pacific-North American relative plate motion is accommodated by offshore strike-slip faulting in the ICB. The Newport-Inglewood Rose Canyon (NIRCFZ) fault complex is a right-lateral strike-slip system that extends primarily offshore approximately 120 km from San Diego to near Newport Beach. Based on trenching and well data, the NIRCFZ system Holocene slip rate is 1.5-2.0 mm/yr to the south and 0.5-1.0 mm/yr along its northern extent. An earthquake rupturing the entire length of the system could produce an Mw 7.0 earthquake or larger. Offshore San Onofre, CA the main segments of the NIRCFZ system jog leftward creating transpressional features resulting in an anomalously wide shelf in this region. West of these segments, the San Onofre Fault Trend (SOT) strikes obliquely along the slope. Previous work concluded that SOT is a part of a strike-slip system that eventually merges with the NIRCFZ complex on the shelf. Conversely, others have interpreted this system as deformation associated with the Oceanside Blind Thrust fault purported to underlie most of the region. In late 2013, we acquired the first high-resolution 3D P-Cable seismic survey (6.25 m bin resolution) of both the NIRCFZ and SOT. These 3D seismic data volumes illuminate the shelf and upper slope at the scale of deformation, and multi-attribute analysis of these data volumes provide important new insights and constraints on fault segmentation and transfer of deformation in this region. Based on the analysis of this 3D seismic data, our preferred interpretation for SOT is a set of transpressional features associated with leftward jogs along right-lateral fault strands splaying off and eventually converging with the NIRCFZ system northwest of the widest part of the shelf

Plain Language Summary. The Newport-Inglewood Rose Canyon fault system is a large collection of earthquake faults that run offshore of Southern California from San Diego to Newport Beach. The San Onofre Fault Trend is a group of smaller earthquake faults that approach the continental shelf near San Onofre, California. Using state-of-the-art 3D geophysical tools, we have created high-resolution 3D maps of geologic structures under the sea floor that were created by these faults. With these new maps, we provide an analysis of how these fault segments interact to distribute strain, and the crustal deformation that is created in the process. This data provides us with new insight into the hazard risk of these faults to coastal residents

Peer reviewed