Pseudo-elastic pure P-mode wave equation

We present a pseudo-elastic wave equation describing pure pressure waves propagating in elastic media. The pure pressure-mode (P-mode) wave equation uses all the elastic parameters (such as density, P- and S-wave velocities). It produces the same amplitude variation with offsets (AVO) effects as the PP reflections computed by the conventional elastic wave equation. Because the new wave equation is free of shear waves, it does not require finer grids for simulation. This leads to a significant computational speedup when the ratio of pressure to shear wave velocities is large. We tested the performance of our method on a simple synthetic model with high-velocity contrasts. The amplitude admitted by the pseudo-elastic pure P-mode wave equation is highly consistent with that associated with the conventional elastic wave equation over a large range of incidence angles. We further verified the proposed method's robustness and accuracy using a more complex and realistic SEAM 2D salt model. The ideal AVO behavior and computational advantage make the proposed wave equation a good candidate as a forward simulation engine for performing elastic full-waveform inversion, especially for marine streamer datasets.