Surface Topography Effects on Lg Wave Propagation in Heterogeneous CrustalWaveguides

摘要

The object of this research is to study the effects of surface topography, nearsurface (sedimentary) structure and the associated small scale heterogeneities on regional wave propagation which is critical for both discrimination and yield estimation in monitoring a Comprehensive Test Ban Treaty and the current Nuclear Non-Proliferation Treaty. We aim at developing a hybrid method which couples the recently developed fast screen propagator theory and methods (Wu, 1994; Wu and Xie, 1994; Wu and Huang, 1995) with a modified Boundary Integral Equation (BIE) method to treat the influences of both volume heterogeneities and irregular interfaces, including the influence of surface topography. We adopt Chen's Global Generalized Reflection/Transmission Matrix (GGRTM) method as the major element in our hybrid method. As the first step, we test both the generalized screen one-way wave method and the GGRTM method, and develop the connection of the two algorithms for the two-dimensional SH case. Chen's theory has been modified for this purpose and the connection formulas have been derived and numerically tested. The excellent agreement between seismograms for direct propagation and propagation using the connection formulas proves the correctness of the theory and the feasibility of the methodology.