Inner California Borderland High-Resolution Fault Mapping: Rose Canyon Fault Releasing Stepover in San Diego Bay Pull-apart Basin

Andrea Fabbrizzi, Eui-jo D. Marquez, Drake M. Singleton, Jillian M. Maloney, Thomas K. Rockwell, Neal W. Driscoll, & Scott Rugg

Published September 11, 2022, SCEC Contribution #11975, 2022 SCEC Annual Meeting Poster #132 (PDF)

Poster Image: 
The releasing stepover in San Diego Bay is characterized by a pull-apart basin geometry between the southern termination of the Rose Canyon fault around downtown San Diego and the Descanso fault offshore along the USA-Mexico coastline. Although the step between these two strike-slip faults is considered too large for through-going rupture, the complexity of fault segments within the San Diego Bay pull-apart basin is not well defined and might considerably increase the seismic hazard for the city of San Diego. We use a combination of geophysical techniques (multi-channel seismic, Chirp sub-bottom, multibeam bathymetry) and onshore geotechnical surveys to create a novel fault model of the northern San Diego Bay pull-apart basin. We estimate Holocene active deformation of the Spanish Bight fault, East Bay fault, and Harbor Island fault with fault-related bay floor deformation. Further, we calculate subsidence rates between 0.15 and 0.21 mm/yr around the San Diego International airport, accommodated by the East Bay fault, and observe overall transtensional kinematics with down-to-the-east displacement. The fault model proposed in this work contributes to determining the San Diego Bay pull-apart basin evolution, understanding the mechanisms driving slip transfer and earthquake propagation across the releasing stepover, and increasing the resolution of Southern California rupture forecast models.

Key Words
San Diego Bay, Fault geometry, Releasing stepeover

Citation
Fabbrizzi, A., Marquez, E. D., Singleton, D. M., Maloney, J. M., Rockwell, T. K., Driscoll, N. W., & Rugg, S. (2022, 09). Inner California Borderland High-Resolution Fault Mapping: Rose Canyon Fault Releasing Stepover in San Diego Bay Pull-apart Basin. Poster Presentation at 2022 SCEC Annual Meeting.


Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)