Forward modeling the origin of seismic anisotropy at the base of the mantle

The goal of this research is to investigate seismic anisotropy and velocity boundaries in the D’’ region by combining mineral physics, geodynamics and seismic modeling. Strain evolution through the D’’ is tracked by tracers in a mantle convection model. To predict anisotropic tensors, texture is calculated and elastic constants are averaged. In this step different hypothetical mineral assemblages, combining perovskite, postperovskite and magnesiowustite, and slip systems are tested. Possible 1D models and 3D models of a slab are implemented in a Coupled Spectral Element Method. CSEM couples the spectral element part in the lower mantle to a computationally faster 1D normal mode solution in the rest of the Earth. Synthetic results calculated down to ~10s will be presented here. The nature and characteristics of the synthetic Sdiff and ScS waves are compared with real observations as a function of distance and azimuth. Recently the coverage of observations beneath the Pacific has been greatly improved by the Transportable Array. An important step before interpreting is to correct the S-wave phases for anisotropy occurring in the upper mantle.