Toomey, DouglasFerragut, Gabriel2022-02-182022-02-182022-02-18https://hdl.handle.net/1794/27042The Mendocino Triple Junction (MTJ) joins the Gorda, Pacific, and North American plates and migrates northward leaving the San Andreas Fault in its wake. This affects subduction-related stress conditions that control megathrust locking, slab window formation, and asthenospheric upwelling at the southern terminus of the Cascadia Subduction Zone (CSZ). These geologic variables impact earthquake hazards and remain relatively poorly understood. Constraining them requires a high-resolution multi-scale 3D seismic imaging approach using local and teleseismic earthquakes as well as active-source data. Yet active-source data near the MTJ is decades old, incomplete, and inconsistent in its metadata. To facilitate future multi-scale seismic imaging of the MTJ, we rescue archived active-source data, resulting in a dataset usable for modern 3D tomography. Forward modelling shows varying but generally high misfit (1ms to >1s), indicating additional structure exists not accounted for in the model, but which may be resolved in future multi-scale inversions.en-USAll Rights Reserved.GeophysicsLegacy DataMendocino Triple JunctionSeismologyTomographyElectronic Thesis or Dissertation