Phase unwrapping of angle-domain common image gathers |

Migration velocity analysis is a class of techniques used for updating the velocity field, starting from a migrated image. These techniques are based on linking the curvature of image gathers (for instance Angle-Domain Common Image Gathers) to migration-velocity error. When this relation is linearized, it leads to a simple inversion problem. However the linearization of the wave field with the first-order Born approximation comes with an important limitation: it can handle delays only up to a fraction of the wavelength.

This problem has been given a possible solution in Sava and Biondi (2004). A viable alternative is to transform the ADCIGs to the Fourier domain and do phase unwrapping there, which is roughly equivalent to determining the delay in the original domain. This is suggested in Sava and Biondi (2003) concerning the Rytov approximation. Synthetic Aperture Radar Interferometry and Magnetic Resonance Imaging literature offers many examples of unwrapping techniques. Although they share common principles, each one must be carefully tuned to the specific application.

In this paper we adapt a phase-unwrapping algorithm to unwrap ADCIGs. We describe how to formulate the unwrapping problem, solve it, and test it on a simple synthetic case. We show that by unwrapping jointly several gathers we can overcome some sampling limitations in the angle domain.

Phase unwrapping of angle-domain common image gathers |

2007-09-18