Fault Deformation and Segmentation of the Newport-Inglewood Rose Canyon, and San Onofre Trend Fault Systems from New High-Resolution 3D Seismic Imagery

James J. Holmes, Neal W. Driscoll, & Graham M. Kent

Published August 15, 2016, SCEC Contribution #6935, 2016 SCEC Annual Meeting Poster #107

The Inner California Borderlands (ICB) is situated off the coast of southern California and northern Baja. The structural and geomorphic characteristics of the area record a middle Oligocene transition from subduction to microplate capture along the California coast. Marine stratigraphic evidence shows large-scale extension and rotation overprinted by modern strike-slip deformation. 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 farthest inshore fault system, the Newport-Inglewood Rose Canyon (NIRC) Fault
is a dextral strike-slip system that is primarily offshore for approximately 120 km
from San Diego to the San Joaquin Hills near Newport Beach, California. Based on trenching and well data, the NIRC Fault 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.

West of the main segments of the NIRC Fault is the San Onofre Trend (SOT)
along the continental slope. Previous work concluded that this is part of a strike-slip system that eventually merges with the NIRC Fault. 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 Parallel Cable (P-Cable) seismic surveys of the NIRC and SOT faults as part of the Southern California Regional Fault
Mapping project aboard the R/V New Horizon. Analysis of these data volumes provides important new insights and constraints on the fault segmentation and transfer of deformation.

Based on this new data, we’ve mapped several small fault strands associated with the SOT that we observe to link up with a westward jog in the NIRC Fault on the shelf. Our observations are that these strands are strike-slip features associated with a dying splay of the NIRC system rather than compressional features associated with a regional thrust.

Key Words
deformation, earthquakes, seismic, 3d, reflection, fault, thrust, geology, san onofre, southern california, high resolution

Citation
Holmes, J. J., Driscoll, N. W., & Kent, G. M. (2016, 08). Fault Deformation and Segmentation of the Newport-Inglewood Rose Canyon, and San Onofre Trend Fault Systems from New High-Resolution 3D Seismic Imagery. Poster Presentation at 2016 SCEC Annual Meeting.

Related Projects & Working Groups
Earthquake Geology