Joint inversion of normal mode and body wave data for inner core anisotropy 1. Laterally homogeneous anisotropy

Abstract

We use mantle and inner core sensitive normal modes to invert for laterally varying mantle models and a transversely isotropic inner core. To obtain an inner core model that is compatible with long‐period mode and short‐period body wave data, we incorporate mantle‐corrected absolute travel time and differential travel time data in our inversions. Using this diverse data set, we investigate the dependence of inner core models upon mantle parameterization and possible radial structure within the inner core. Inner core anisotropy obtained from a simultaneous inversion for mantle and inner core structure has a weak dependence upon the parameterization within the mantle, that is, the results for the inner core are insensitive to whether the mantle is inverted only for shear velocity structure or for shear and compressional velocity structure as well as density. An inner core model with constant anisotropy is capable of fitting all types of data, but mode and absolute travel time data are more compatible with one another than with differential travel time data. Allowing for radial variations within the inner core reduces this incompatibility, and it is possible to obtain a radially dependent model that fits normal mode, absolute travel time, and differential travel time data with a variance reduction greater than 75%.