This research will study three widely separated areas of the earth with a common thread of theoretical waveform modeling that has been developed by earlier studies. Seismic body waves will be synthesized using approximate high frequency and hybrid approximate/finite difference techniques and compared to data waveforms to investigate characteristics from three zones: 1) the thickness, mantle penetration, and stratification of descending lithospheric slabs; 2) the heterospectrum of the lowermost D" region of the mantle and topography of the core-mantle boundary; and 3) the lateral variation and anisotropy of the elastic and anelastic structure of the inner core. The results of this research will include evidence for the existence or nature of slab penetration below 650 km; a test of the origin of a high frequency waveguide along the top of some slabs; a test of the applicability of the Born approximation to the study of PKIKP precursors and the importance of strong scattering within D"; and a test of an anelastic model of the inner core as an explanation for the observed amplitude, travel time, and frequency content for PKIKP.
