Attenuation of P and S waves diffracted around the core

A comparison of observed decay spectra of diffracted P and SH waves, with theoretical results for a standard (PEM-C) model, reveals characteristic differences between P and SH, and between observational and model data. As a prerequisite to a joint interpretation of these characteristics, the effects of various realistic structures near the core-mantle boundary (CMB) are formulated and quantified. The following possibilities are considered: (1) velocity gradients in the mantle, (2) density and velocity contrasts across CMB, including the possibility of rigidity in the core, (3) anelastic damping, (4) scattering by a rough CMB, (5) scattering by heterogeneity in the mantle above CMB. Specific conclusions with regard to the effects of admissible changes in each of these model parameters are given in appropriate sections of the paper. Generally, the effects are different for P, SH and SV and the results indicate that, when taking these effects into account, the resolution of velocity structure at the base of the mantle can be significantly improved by a joint inversion of P and S diffraction data.