Comparison of irregular cartesian finite difference methods for acoustic RTM

We compare three Irregular Cartesian Finite Difference (ICFD) methods towards deployment into Forward Modeling and RTM. The ICFD methods considered are based on: Forn-berg (1988), Gamet et al. (1999) and Pitarka et al. (1999). These methods consist of providing a two-way acoustic wave propagation adapted to the P-wave velocity field. While respecting stability and low numerical dispersion criteria, they avoid the spatial oversampling introduced by a uniform spacing. Thus they reduce in a significant manner the required computer memory and execution time. We show in examples that ICFD methods allow to obtain results as accurate as high-order Regular Cartesian Finite Difference methods. Also, we evaluate the accuracy and the performance of the non-uniform stencil computation for each of the three ICFD methods. Finally, we validate that ICFD methods provide significant speed-up for FD propagators-based applications.