I show in this chapter that the residual moveout equation of a 3D specular water-bottom multiple from a flat water-bottom in 3D ADCIGs is a direct extension of the 2D equation presented in Chapter after a simple rotation of coordinates to account for the source-receiver azimuth. The raypath of the specular water-bottom multiple in this case is confined to one vertical plane and is therefore essentially a 2D multiple. For a water-bottom that dips in the inline direction only, the raypath of the multiple is contained in a vertical plane only if the source-receiver azimuth is in the inline direction. For other directions, and for all directions if the water-bottom dips in the crossline direction, however, the propagation of the multiple is not contained in a plane.
In this chapter I concentrate on the mapping of the multiples to image space and leave their attenuation for later chapters. I will illustrate the mapping of the water-bottom multiple from a water-bottom dipping in the crossline direction using a very simple 3-D synthetic prestack dataset provided by ExxonMobil.