Improved Strategies for Seismically Imaging Earth's Anisotropic Interior with Applications to Subduction Zones and Volcanic Systems

Seismic anisotropy -- the directional dependence of seismic wave speeds -- provides a unique view into the past and present deformation of Earth's interior. However, constraining Earth's anisotropic heterogeneity remains a challenge primarily due to imperfect data coverage combined with the increased number of free parameters required to describe elastic anisotropy. And yet, exploring this more complex model space is critical for the interpretation of seismic velocity anomalies which may be significantly distorted if anisotropy is neglected. In this presentation, I will review new imaging strategies, developed by myself and colleagues, for constraining 3D anisotropic structures and their application to studying subduction zone dynamics and volcanic processes. Key developments include moving beyond simplified assumptions regarding the orientation of anisotropic fabrics (i.e. from azimuthal and radial parameterisations to tilted-transversely isotropic models), the integration of multiple and complementary seismic observables (P and S body wave arrivals, shear wave splitting measurements, and surface wave constraints), and the use of probabilistic inversion algorithms that allow for rigorous exploration of model uncertainty and parameter trade-offs. I will discuss how applying these imaging approaches to subduction systems in the central Mediterranean and Western USA yields new insights into the geometry of mantle flow, the nature of seismic velocity heterogeneity, and trade-offs between isotropic and anisotropic features. At smaller scales, I will highlight how new anisotropic tomography reveals the structure of the magmatic plumbing system beneath Mt. Etna (Italy) and provides constraints on the geologic processes controlling crustal stresses.