Fluid-Abundant Subduction–Transform Fault Interactions During the 2024 Mw 7.0 Mendocino Earthquake

Jinzhi Ma, Elizabeth Su, Liuwei Xu, & Lingsen Meng

Submitted September 7, 2025, SCEC Contribution #14282, 2025 SCEC Annual Meeting Poster #TBD

The 2024 Mw7.0 Mendocino earthquake struck at the junction of the Mendocino transform fault and the Cascadia subduction zone, near the Mendocino triple junction. It was the largest earthquake in over three decades. Using advanced earthquake catalog construction, finite-fault inversion, and backprojection techniques, this study describes the earthquake sequence from foreshocks to the mainshock and aftershocks. Results indicate that mainshock nucleation was driven by diffusion of shallow fluids in the subduction zone, with seawater infiltration—though less likely—possibly contributing to initiation. The slow rupture of the mainshock, accompanied by high-frequency radiation, suggests that fluids were involved throughout the rupture. Aftershocks with pronounced thrust components and the double-seismic-zone morphology reveal the release of residual slip on the subduction interface. Continuous fluid input and interaction between the transform fault and subduction zone increase shallow-fault rupture potential, raising seismic hazard and offering insights for other fluid-rich subduction margins.

Key Words
Mendocino earthquake, Transform fault, Fluid, Subduction zone

Citation
Ma, J., Su, E., Xu, L., & Meng, L. (2025, 09). Fluid-Abundant Subduction–Transform Fault Interactions During the 2024 Mw 7.0 Mendocino Earthquake. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Seismology