Wave-equation migration techniques have benefited from a renewed interest now that some shortcomings of Kirchhoff migration have been highlighted O'Brien and Etgen (1998). Moreover, intensive computing resources now make 3-D prestack depth migration feasible with such techniques. Based on a recursive extrapolation of the recorded wavefield, wave-equation migration methods are potentially better able to handle multi-pathing problems induced by complex velocity structures. Thus, they offer an attractive alternative to Kirchhoff methods Biondi (1997); Mosher et al. (1997). Moreover, wave propagation is modeled out of the asymptotic approximation context.
Common-azimuth migration Biondi and Palacharla (1996) is a 3-D
prestack depth migration technique based on the wave equation. It
exploits the intrinsic
narrow-azimuth nature of marine data to reduce its dimensionality and
thus manages to cut the
computational cost of 3-D imaging significantly. In this paper, we
discuss the first
application of this imaging technique to real data at SEP. For this
purpose, Elf Aquitaine provided us with an
interesting dataset recorded in the North Sea, which shows a salt dome
3-D structures. The complexity of the wave propagation in the medium, resulting from high velocity contrasts (lateral and longitudinal), yields multi-pathing and illumination problems, which makes this model both a serious challenge for imaging and an interesting test case for the common-azimuth migration.