A 2-D synthetic study of global traveltime tomography

A 2-D synthetic test study of global traveltime inversion for deep seated earth structure has been undertaken. This was done by generating traveltime residual data using reasonable models for earth structure. The data were then inverted by similar methods to those applied in global studies of earth structure. Our results indicate that models of the aspherical structure in the lower mantle based on traveltime data are only partially successful and only at the largest scales (harmonic degree ≤3) and that maps of the core—mantle boundary based on traveltimes are unsuccessful.