SCEC Award Number 24183 View PDF
Proposal Category Individual Research Project (Single Investigator / Institution)
Proposal Title Earthquake Relocation in the Mendocino Region of Northern California
Investigator(s)
Name Organization
Susan Bilek New Mexico Institute of Mining and Technology
SCEC Milestones D1-1, A2-3, A3-2 SCEC Groups Seismology, PBS, FARM
Report Due Date 03/15/2025 Date Report Submitted 03/14/2025
Project Abstract
 The Mendocino triple junction (MTJ) region is one of the most seismically active areas of California, with least 40 earthquakes of magnitude 6 or larger in the region over the past 100 years (e.g. Dengler et al., 1992; USGS, 2023), including events in 2021 and 2022 near the Ferndale, CA region that produced widespread power disruptions and damage (USGS, 2023; Stein et al., 2023). These earthquakes are associated with the interactions of the Pacific, Gorda, and North America plates, bringing together subduction and transform plate boundaries in a complex zone of deformation. Recent efforts have used numerous onshore and offshore seismic stations to detect small magnitude earthquakes occurring in region, largely focused on initial detection and location of the events (Alongi et al., 2021; Morton et al., 2023). The primary objective of our research project was to relocate the portion of the large Morton et al. (2023) earthquake catalog covering the Mendocino region (3,983 events) using the GrowClust algorithm (Trugman et al., 2022) in order to better characterize the complex faulting in this MTJ region. Focusing on the years 2012-2013 and 2014-2015, we relocated a total of 2408 earthquakes, the majority of which occurred in the MTJ region, with small numbers located along the Mendocino fracture zone as well as further north along OR.
Intellectual Merit The project resulted in high-quality earthquake locations in the complex Mendocino triple junction faulting region. Our findings suggest that even the relocated events are complex, especially during 2014-2015 period, where no clear spatial patterns are clearly visible, potentially suggesting the need for improved velocity models and continued monitoring to better image which structures are responsible for the seismicity in this region.
Broader Impacts Through this project I was able to hire and train an undergraduate student who had no previous seismology or geophysics research exposure. She developed computing skills (unix, matlab, julia) that she will in her upcoming graduate degree program at the University of New Mexico.
Project Participants Dr. Susan Bilek
Ms. Vennessa Maestas
Exemplary Figure Figure 5: Earthquake locations within the MTJ region, format same as Figure 4. Top: Year 2, bottom: year 4. Green stars show USGS locations of earthquakes with magnitude > 6.5 since 1954, including the 2024 M 7 event along the Mendocino fracture zone.
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