“…They also provide necessary wavefield solutions for imaging (especially, reverse time migration) and full waveform inversion. Many numerical methods have been proposed to solve wave equations, among which the finite-difference method has been a popular choice (e.g., Kelly et al, 1976;Virieux, 1984Virieux, , 1986Levander, 1988;Faria and Stoffa, 1994;Igel et al, 1995;Wu et al, 1996;Saenger and Bohlen, 2004;Etgen and O'Brien, 2007). Another commonly used method is the pseudospectral method (e.g., Gazdag, 1981;Kosloff and Baysal, 1982;Kosloff et al, 1984;Fornberg, 1987;Reshef et al, 1988aReshef et al, , 1988bCarcione et al, 1992;Carcione, 1999).…”