SCEC Award Number 25265 View PDF
Proposal Category Individual Research Project (Single Investigator / Institution)
Proposal Title Marine geohazard assessment in the Outer California Borderland: fault network and mass wasting investigation
Investigator(s)
Name Organization
Jillian Maloney San Diego State University Andrea Fabbrizzi San Diego State University
SCEC Milestones A1-1, A1-3, A2-2, A3-1, A3-4 SCEC Groups Geology, PBS, CCB
Report Due Date 03/15/2026 Date Report Submitted 06/02/2026
Project Abstract
 We completed high-resolution mapping of faults and submarine landslides in the Outer California Borderland (OCB), offshore from southern California. Offshore active fault systems and submarine landslides pose a major hazard to infrastructure and high density coastal areas, while being little researched and difficult to study. Southern California's coastal communities may be impacted by offshore faults through earthquakes and tsunami waves they may generate. Furthermore, submarine slumps and debris slides can also produce tsunamis with equally devasting long-range impacts. The California Continental Borderland (CCB), which constitutes the westernmost portion of the Pacific North American plate boundary across southern California, is an ideal location to research the complex relationship between active fault systems and seafloor mass wasting. We conducted comprehensive geophysical mapping and characterization of faults and mass transport deposits (MTDs) in the OCB to assess the relationship between mass wasting and seismicity. We combined existing data from Cortes Basin and Velero Basin, with data from two additional research cruises covering San Nicolas Basin, Tanner Basin, San Clemente Basin, and the Ferrelo fault zone. Our results include detailed fault mapping across several basins with newly mapped and recently active faults, and mapping and characterization of MTDs in several basins. The data from the most recent research cruise (February 2026) are still being analyzed but will eventually contribute to a comprehensive dataset for the region. Results were published in JGR Solid Earth and Marine Geology and supported one MS thesis, one undergraduate thesis, and two undergraduate research projects.
Intellectual Merit This research identified repeated MTDs of varying morphology in the OCB, suggesting that low slip-rate offshore faults along California’s transform plate boundary are capable of trigging submarine landslides. As such, the repeated MTDs may be useful for reconstructing the paleoseismic history of fault zones in a region where other methods are ineffective.
Broader Impacts This project supported teaching, training, and learning at SDSU through student participation in the research process. This includes the participation of 15 undergraduate, 4 MS, and 2 PhD students as science crew between the two cruises, an MS Thesis, and a BS Thesis. Additionally, the identification of recently active faults and the potential for earthquake triggered submarine landslides has implications for geohazard assessment in southern California.
Project Participants Andrea Fabbrizzi, postdoctoral researcher, contributed to data collection, processing, and interpretation and published two peer-reviewed papers; Alicia Sigworth, MS student, contributed to data collection, processing, and interpretation and completed an MS Thesis; Glenn Jenkins, BS student, contributed to data collection, processing, and interpretation and completed a BS Thesis; UC Ship Funds awarded ship time aboard the R/V Sally Ride, the R/V Sally Ride crew operated the ship to achieve our scientific objectives; BS, MS, and PhD students from SDSU contributed to data collection and processing aboard the research cruises.
Exemplary Figure Figure 2. High-resolution geophysical data synthesis from our R/V Sally Ride cruises SR2303, SR2502, and SR2602, compiled to demonstrate the exceptional quality and coverage of the collected datasets, and illustrate some of the significant findings. The figure highlights bathymetry and sub-bottom profiler data, showing the ability to resolve fault offsets, multiple types of MTDs, and the relationships between faulting and MTDs.
Linked Publications

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