9725496 Dahlen This research involves the development, testing, and exploitation of methods of inferring the lateral heterogeneity of the earth at intermediate scales, using 3-D Frechet kernels. Current instantaneous kernels will be extended to higher ray parameters by allowing for the coupling of more surface-wave overtone branches. Mode-ray duality will be explored by comparing coupled surface-wave kernels with kernels based upon body-wave JWKB theory. Three- dimensional kernels will be developed for wave-form functionals such as travel-time residuals measured by cross-correlation of observed and spherical-earth synthetic seismograms. Several other theoretical developments will be undertaken to implement the development of improved earth models from the greatly improved broad-band data sources such as the Global Seismic Network and the portable PASSCAL array projects. The improved earth models are essential to investigation of the driving forces of plate tectonics, the energy source for earthquakes. This research is a component of the National Earthquake Hazard Reduction Program. ***
