Scattering Of Elastic Waves By Alpine Gorge And Basin Mountain Coupled Sites

Scattering and diffraction of the seismic waves by the irregularities is a hot research topic in the fields of seismic engineering.In the existing research,the analyses of the local sites mainly focus on the single model.There are few intensive studies about the much more complex topographies.However,many major traffic projects,largescale communication equipment and ultra-high buildings have been planned in complex alpine gorge and basin mountain coupled sites in recent years,and the seismic fortification requires the reliable earthquake analyses.Therefore,great theoretical meaning and engineering values should be attached to the study of the scattering and diffraction problem of seismic waves by complex coupled topographies.The indirect boundary element method(IBEM)is adopt to study scattering of elastic waves by complex local sites in this paper.The main contents are listed as follow:1.Scattering of elastic waves by alpine gorge sites.Based on the exact dynamic stiffness of layered half-space,the half-space Green's function of horizontal line is derived by using direct stiffness method.The IBEM is proposed by using the half-space Green's function of horizontal line,half-space Green's function of inclined line and full-space Green's function as fundamental solutions.By decomposing the whole model in reasonable way,the advantages of half-space Green's function and full-space Green's function can be fully utilized.The effective of calculation is significantly improved.The approach is verified by comparing the degenerated results with the existing ones,and numerical calculations are performed in frequency domain and time domain to study the scattering of plane P and SV waves by alpine gorge sites in the homogeneous and single layered half-space.2.Scattering of elastic waves by 3D basin mountain coupled sites.By introducing a virtual semi-ellipsoid surface near the irregularity,the whole model can be decomposed into hill closed regions,valley closed region,additional closed region and semi-ellipsoid opened half-space region.The scattered fields in closed regions are calculated by full-space Green's function,and the scattered fields in opened regions are calculated by half-space Green's function combined with the rotation symmetry.Therefore,the effective of calculation is significantly improved.The approach is verified by comparing the degenerated results with the existing ones,and numerical calculations are performed in frequency domain to study the scattering of plane P,SV and SH waves by 3D basin mountain coupled sites in the homogeneous and single layered half-space.The numerical results indicate that the changes of the mountain height of the alpine gorge and basin mountain coupled sites have a significant effect on the spatial distribution of the surface displacement amplitude near the local sites;mountain has a blocking effect on the obliquely incident waves,and the higher mountain can cause the more obvious effect,the peak value of displacement amplitude of the canyon or basin in the case of high mountain is only 60%~80% of the corresponding one in the case of low mountain;the existence of bedrock will significantly change the dynamic interaction mechanism between different parts of the topography,leading to the significant changes of the scattering of the elastic waves by the local sites.