Surface Wave-Propagation on a Laterally Heterogeneous Earth

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9505677 DAHLEN This research is to study the propagation of fundamental and higher-mode surface waves in a laterally heterogeneous earth. Previous results will be extended to focus on higher-frequency surface waves, for which cross-branch coupling due to variations in crustal thickness and shorter scale-length variations in the upper mantle such as slabs, become more important. Work will continue with the development of a spline basis on the surface of a tesselated sphere to replace the widely-used spherical-harmonic representation of three-dimensional earth models. Such a local basis has a number of advantages, including the ability to vary the node spacing depending upon the coverage, and a dramatic improvement in the speed of surface-wave ray tracing due to the reduction in the number of evaluations required at each step. This research is a component of the Cooperative Studies of the Earth's Deep Interior program. ***