Transformation to dip-dependent Common Image Gathers

We introduce a new transform of offset-domain Common Image Gathers (CIGs) obtained by wavefield-continuation migration methods. This transformation can be applied to either horizontal-offset CIGs or vertical-offset CIGs. It overcomes the limitations that both kinds of CIGs suffer in the presence of a wide range of reflectors’ dips. The result of our transformation is an image cube that is equivalent to the image cube that would have been computed if the offset direction were aligned along the apparent geological dip of each event. The proposed transformation applies a non-uniform dip-dependent stretching of the offset axis and can be efficiently performed in the Fourier domain. Because it is dependent on the image’s apparent dip, the offset stretching automatically corrects for the image-point dispersal. Tests on a synthetic data set confirm the potential advantages of the transformation for migration velocity analysis of data containing steeply dipping reflectors.