Theory, techniques, and numerical results for retrieval of Earth models (including mantle heterogeneity, topography of the core-mantle boundary (CMB), and inner core anisotropy) are presented. The inversions for Earth models are based upon spectral splitting of 33 isolated multiplets, observed in long-period accelerograms of 10 large events recorded by the International Deployment of Accelerometers network. Approximately 1000 spectra are involved. It is demonstrated that it is possible to obtain large-scale (spherical harmonic degrees s = 0,2,4) models of mantle heterogeneity from such a data set under the constraint that aspherical perturbations in seismic velocities and density are proportional to one another. -from Authors
