Classical Migration Velocity Analysis: The previous imaging methods can be described as estimating the earth model by predicting synthetic data that best explains the observed data in the data domain. In contrast, image-domain inversion finds the velocity model that best explains the observed migration section in the image domain. The observed migration image is obtained by migrating the recorded data using an assumed velocity model. Each iteration of image-domain inversion updates both the velocity model and the migration image. One of the advantages of image-domain inversion is that migration untangles crossing events in the data domain and focuses them to the vicinity of the reflecting boundary. Hence, the migration image should have a higher signal-to-noise ratio (S/N) than the original data for a reasonably accurate velocity model.