The premise of the layer-stripping method is that data can be re-synthesized at any subsurface datum by downward continuation with the adjoint Kirchhoff datuming algorithm. The depth step of the datuming is limited so that the first-arrival traveltimes are calculated in such a way that they accurately parameterize the most energetic portions of the wavefield. In this way, the downward continued data are accurately synthesized at a datum which is closer to the imaging target. Traveltimes can then be calculated from the new datum, and the data can either be downward continued again or migrated from the new datum.
Since all the traveltimes in this process are calculated over a smaller portion of the velocity model, the final outcome is a more accurate image.