This research addresses a broad range of questions related to earth structure and the nature of earthquakes. 3-D velocity structure inversion methods will be tested for the influence of uneven ray-path distribution. 3-D splines will be used to join high-resolution models to global models. Work will continue on the mapping of anisotropic structure in the lithosphere and asthenosphere. A refinement will be done of the mapping of topography for the 410 and 660 km discontinuities. The spatial variation of anisotropy in the inner core will be investigated, especially with respect to its influence on estimates of the super-rotation of the inner core. For earthquakes, the widely used CMT (Centroid Moment Tensor) analysis and "Quick CMT" determination and dissemination will be improved and expanded to multiple-event/smaller earthquake capability, and the low-frequency earthquake source spectrum inversion techniques will be improved. This research is a component of the National Earthquake Hazard Reduction Program.
