Lg Wave Propagation using SH and P and SV Screen Propagators in Heterogeneous Crusts With Irregular Topography
CALIFORNIA UNIV SANTA CRUZ
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This study is aimed at development and application of new wave propagation and modeling methods for regional waves in heterogeneous crustal waveguides using one-way wave approximation. The half-space generalized screen propagators GSP for both SH and P-SV waves have taken the free surface into the formulation and adopt a fast dual domain implementation. The method is several orders of magnitude faster than finite-difference method with a similar accuracy for certain problems. It has been used for the simulation of wave propagation for high-frequency waves 1-25Hz to a regional distance greater than 1000km. In this year, we further develop the method in two fronts. First, we extend the SH GSP method to treat irregular surface topography by incorporating a coordinate transform into the method. It is demonstrated that our new approach has superior wide-angle response to surface topography over the PE parabolic equation method. The efficiency of the screen propagator approach makes it very promising for long distance Lg simulation. For a test model with a propagation distance of 250km and a dominant frequency of 1Hz, the screen method took about 35 minutes, while the boundary element method took about 72 hours. For longer propagation distances and higher frequencies, the factor of saving could be huge. Second, we developed a P-SV screen propagator for crustal waveguides with flat surfaces. This is the major task of this year. Free surface reflection and conversion have been incorporated into the screen propagator theory. Numerical tests have been done against the wavenumber integration and finite-difference calculations. The results demonstrated the feasibility of the approach. Finally, numerical simulations have been conducted for various crustal waveguide structures, including deterministic structures, small-scale random heterogeneities and random rough surfaces.
- Numerical Mathematics
- Seismic Detection and Detectors