Effect of 3-D Heterogeneities and Topography on Seismic Wave Propagation and theUse of Empirical Green's Functions for Source Characterization and Discrimination

摘要

We investigate two topics related to seismic nuclear monitoring anddiscrimination. The first is elastic wave propagation in complex earth models containing lateral variations in elastic properties or irregular interfaces. We describe an improved boundary element technique based on the conjugate gradient method and apply it to study the effects of surface topography. We also investigate the usefulness of a hybrid modeling method that combines multiple multipole and finite element techniques. Additionally, finite difference modeling is applied to a comparison of 2-D and 3-D scattering from irregular interfaces. The second topic area is the development of improved seismic discriminants. We find that the empirical Green's function method is effective for estimating the source time functions of earthquakes and explosions, and that the duration of the source time function is a good discriminant for large and very small events. For small events (M<3) and near regional distances (<250 km), Lg spectral ratio is a good discriminant between earthquakes and industrial explosions.