Joint Refraction Traveltime Migration And Tomography

Migration and tomography represent two major techniques in state-of-the-art seismic imaging technology.<br>Migration maps interfaces in the subsurface by reconstructing physical raypaths from a downward continuation<br>process, while tomography reconstructs a physical model by inverting recorded data. For interpreting<br>refraction traveltimes, we present two approaches that combine migration and tomography in one joint imaging<br>process in an iterative manner. The slowness parameters on a regular grid can be updated on the basis<br>of fitting traveltimes as well as defining interfaces associated with the migrated traveltime image. The first<br>method, model-interface method, assumes that the migration image corresponds to a slowness discontinuity<br>in the model. Therefore, an a priori curvature constraint is emplaced at the image location by way of<br>Tikhonov regularization. The second approach places a discontinuity in the regularization (Laplacian) operator<br>according to the location of the migration image, thus it is called derivative-interface method. The first<br>method gives a stronger model constraint, while the second one relies more on the data. We demonstrate<br>that both methods are capable of reconstructing a reliable velocity model with sharp features.