SUMMARY

In structurally complex media, the accurate recovery of the angle-dependent reflectivity function requires the use of an elastic prestack migration technique. Mode separation can be done before depth extrapolation or during the imaging step. Though more complex, the latter is more complete because it allows the imaging of mode-converted waves. The standard crosscorrelation criterion to implement the imaging condition is not suitable for true reflectivity recovery, especially when imaging reflectivities associated with mode-converted waves. Two new alternative criteria were defined to overcome the limitations of correlation-based imaging conditions. The V-stack criterion accounts for conversion losses of the downgoing wavefield and avoids the imaging of false events associated with an unsmoothed background velocity model. In addition to these advantages, the plane-wave decomposition criterion is designed to generate images that can be directly related to the Zoeppritz equations, since they represent the in-depth plane-wave response of the medium.