2D Rayleigh wave modeling based on MC-PML and its dispersion characteristics analysis
Rayleigh wave modeling is an important tool to understand the law of Rayleigh wave propagation,and it is also the basis of Rayleigh wave inversion.However,in the near-surface high Poisson's ratio seismic modeling,the free-surface boundary method of stress image and second-order velocity evolving case numerical instability when combining the traditional C-PML technology.To overcome this issue,this paper starting from the elastic wave equation,derived the updating formulas of stress component and velocity component under the free-surface boundary condition based on the stress image and second-order velocity expansion method,then,the artificial truncated boundaries at the left and right sides and the bottom of the model are processed by using MC-PML boundary conditions to ensure the computational stability of the coupling region between free boundary and absorbing boundary,finally,Rayleigh wave modeling based on MC-PML is realized by using GPU parallel programming architecture.The results of four typical numerical experiments and dispersion analysis shown that the free-surface treatment scheme of stress image method and second-order velocity expansion combined with MC-PML technology can accurately describe the law of Rayleigh wave propagation,and the MC-PML technology is not affected by the free surface and does not appear numerical instability.The correctness of the key techniques used in the Rayleigh wave modeling is further verified from the high consistency between the peak line of the dispersion energy diagram and analytical solutions of dispersion curves.
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