Calibration of Absorbing Boundary Layers for Geoacoustic Wave Modeling in Pseudo-Spectral Time-Domain Methods

Abstract. This paper develops a calibration methodology of the artificial absorbing techniques typically used by Fourier pseudo-spectral time-domain (PSTD) methods for geoacoustic wave simulations. Specifically, we consider the damped wave equation (DWE) that results from adding a dissipation term to the original wave equation, the sponge boundary layers (SBL) that apply an exponentially decaying factor directly to the wavefields, and finally, a classical split formulation of the Perfectly Matched Layers (PML). These three techniques belong to the same family of absorbing boundary layers (ABL), where outgoing waves and edge reflections are progressively damped across a grid zone of N_ABL consecutive layers. The ABLs used are compatible with a pure Fourier formulation of PSTD. We first characterize the three ABL with respect to multiple sets of N_ABL and their respective absorption parameter for homogeneous media. Next, we validate our findings in heterogeneous media of increasing complexity, starting with a layered medium and finishing with the SEG/EAGE 3-D Salt model. Finally, we algorithmically compare the three PSTD-ABL methods in terms of memory demands and computational cost. An interesting result is that PML, despite outperforming the absorption of the other two ABLs for a given N_ABL value, requires approximately double the computational time. The parameter configurations reported in this article, can be readily used for PSTD simulations in other test cases, and the ABL calibration methodology may be applied to other wave propagation schemes.