Research has been conducted on 3D shear-wave velocity modeling in various regions, including the northern cascadia subduction zone, the tyrrhenian basin, and several other areas around the world. These studies have utilized different methods, such as ambient-noise adjoint tomography and joint inversion of receiver functions and rayleigh wave data, to create 3D models of the crust and upper mantle. The specific focus and findings of the research on the northern cascadia subduction zone are not clear from the available information.