Complex Frequency Shifted Perfectly Matched Layer Boundary Conditions for Frequency-Domain Elastic Wavefield Simulations

To absorb unwanted seismic reflections caused by the truncated boundaries, various absorbing boundary conditions have been developed for seismic numerical modeling in both time and frequency domains. Among the various types of perfectly matched layer (PML) boundary conditions, complex frequency shifted PML (CFS-PML) has attracted much attention in time-domain wavefield simulations because it can better handle evanescent and grazing waves. In this paper, we extend the CFS-PML boundary condition to frequency-domain finite-difference seismic modeling, which has several advantages over time-domain modeling including the convenient implementation of multiple sources and a straightforward extension of adding attenuation factors. A comparison with an analytical solution is used to investigate the validity of the proposed CFS-PML algorithm. CFS-PML shows better absorbing behavior than the classical PML boundary condition in our model tests. We further implement CFS-PML for seismic wavefield simulations in an elongated elastic model and a complex model (Marmousi-II) with a free surface boundary condition.