A Robust Absorbing Layer Method for Seismic Wave Simulation in Anisotropic Media

Seismic wave modeling requires using adapted boundary conditions to simulate infinite or semi-infinite media. Because of its efficiency, the Perfectly Matched Layers (PML) method has rapidly become the standard for acoustic and elastic propagation. However, PML are not adapted to anisotropic media for which the method becomes amplifying. Alternative methods have to be designed. In this study, we present the SMART layer method, which relies on a diagonal decomposition of the hyperbolic operator. The method is not perfectly matched, therefore less efficient than the PML method, however it is proved to remain dissipative, even for anisotropic media. We apply the method to the acoustic TTI equations. We present numerical results on a homogeneous test case and on the BP 2007 model, which includes a space dependent tilt angle. We compare the SMART and the PML methods. The results emphasize the robustness of the SMART method: no wave amplification is observed. In addition, the accuracy of the PML can be reached at the expense of an increase of the SMART layer width. The additional computational cost is compensated by the simple form of the SMART layer: only a zero-order term is added to the equations and no additional variables are required