The authors would like to thank Elf Aquitaine for providing the data and the velocity model and the research group of the Ecole des Mines de Paris for sharing their results with us. Sincere thanks to Bob Clapp as well, who concurrently developed an upgraded version of SEPlib3D that can now handle huge 3-D datasets and made this study possible. We would like to acknowledge Biondo Biondi for his useful comments and stimulating discussions.