Dynamics of the Upper Mantle in Light of Seismic Anisotropy

Seismic anisotropy records continental dynamics in the crust and convective deformation in the mantle. Deciphering this archive holds huge promise for our understanding of the thermo-chemical evolution of our planet, but doing so is complicated by incomplete imaging and non-unique interpretations. Here, we focus on the upper mantle and review seismological and laboratory constraints as well as geodynamic models of anisotropy within a dynamic framework. Mantle circulation models are able to explain the character and pattern of azimuthal anisotropy within and below oceanic plates at the largest scales. Using inferences based on such models provides key constraints on convection, including plate-mantle force transmission, the viscosity of the asthenosphere, and the net rotation of the lithosphere. Regionally, anisotropy can help further resolve smaller-scale convection, e.g., due to slabs and plumes in active tectonic settings. However, the story is more complex, particularly for continental lithosphere, and many systematic relationships remain to be established more firmly. More integrated approaches based on new laboratory experiments, consideration of a wide range of geological and geophysical constraints, as well as hypothesis-driven seismological inversions are required to advance to the next level.