9304492 Romanowicz This research is to model global lateral heterogeneity in the mantle from long-period body waveforms, using a more adequate theory than employed until now in inversions of long-period body waves. The theory takes a normal mode approach which differs from previous ones in that the cross-branch coupling is considered. The theory is accurate within the great-circle section defined by the source and receiver and able to bring out the ray character of long-period body waves. Focusing and defocusing effects within the great-circle section are automatically taken into account. It uses an asymptotic approximation to treat the effect of lateral heterogeneity in the direction perpendicular to the great circle, as done implicitly in all the previous inversions of long-period body waves. A computationally practical inversion algorithm has been set up and tested. It will now be applied to the global long- period digital data set starting with SH and then extending to P- SV cases. ***
