Diffraction Of Plane SH Waves By A Wedge-Shaped Medium With A Circular Canyon Or Alluvial Valley

Site response problem is one of the most important subjects in earthquake engineering. A lot of investigations of earthquake damage show that the existence of local sites affects the scattering and diffraction of seismic wave greatly. Hence, there is sensitive variation of earthquake response of ground surface, underground structure and buildings in narrow spatial dimension. Therefore, the investigation of this kind of problem has important meaning on both theory research and practical project.Wedge site is a sort of common topography in practical project. For the case of Plane SH-Waves incidence ,The wave propagation behavior in an elastic wedge-shaped medium, with a circular canyon or a circular alluvial valley at its vertex, has been separately studied in this thesis. Fourier-Bessel series expansion is used to solve the problem. Two very big circles are used to simulate the free boundary and Graf's addition theorem is used to convert the coordinates. Finally, the unknowns are resolved on the basis of the boundary conditions and the surface displacement is obtained.The analysis demonstrates that the amplification of incident wave almost occurs around the vertex of the wedge due to the influence of the canyon or the alluvial valley. The resulting surface displacement profile depends on numerous parameters, including angle of the wedge, the frequency of incident wave, the material properties of the medial and the angle of incidence. Furthermore, the accuracies of the numerical results are checked by the convergence of the ground surface displacement and residual errors of boundary conditions with the increasing progression term. Compared with the accurate Analytical Solution, it proves that the analysis method used in this thesis is accessible. However, as for the incident P,SV wave,it deserves further study for the complication of the problem.