Introduction

Prestack migration is necessary before AVO analysis. Most of the present migration algorithms not only try to focus the reflections on the subsurface but also strive to preserve the amplitude for subsequent amplitude studies. A migration/inversion method developed by Lumley 1993 estimates the angle dependent reflectivity at each subsurface point by using least-squares Kirchhoff migration followed by a linearized Zoeppritz elastic parameter inversion for relative contrasts in compressional and shear wave impedance. Another migration algorithm is based on the wave-equation method which uses the Double Square Root equation (DSR) for downward continuation. Migration methods based on DSR operators have been applied to 2-D prestack migration for a long time Claerbout (1984) . Only recently computationally efficient methods to continue 3-D prestack data have been presented Biondi and Palacharla (1995). The objective of this paper is to compare the results of the above two algorithms.

The data are taken from the gas hydrate region in Blake Outer Ridge on offshore Florida In a previous study Ecker (1998), the prestack migration is performed with the Kirchhoff migration/inversion. In this paper the same prestack data is migrated by the DSR wave-equation migration as explained in Prucha et al1999.

 

Vel-hydrate-paper
Figure 1 The velocity model used for the two migration methods.