Studies of regional wave propagation using differential seismograms and randomized structural models

In order to improve our abilities to discriminate low yield nuclear explosions and to obtain accurate yield estimates, a study has been undertaken to infer detailed source and structural parameters by direct inversion of broad band seismic data using laterally homogeneous forward modeling methods. Three key problems have been identified which must be solved: the development of an accurate and efficient algorithm for computing differential seismograms, which are necessary for the inversion procedure, the development of better methods for incorporating anelastic attenuation into modal synthesis computations, and the determination of starting solutions that will produce synthetic seismograms which have the same general characteristics that we see in the data. An exact differential seismogram algorithm has been developed and implemented which produces accurate differential seismograms at arbitrary frequencies and phase velocities. An exact complex pole based algorithm has been developed to account for anelastic attenuation. A new representation of earth upper mantle and crustal structure has been used which provides an explainable, plausible and implementable method for modeling the features that we see in regional broad band data.