Focusing operator inversion

The CFP velocity estimation that is described in this report is based on a separated inversion method, in which first the focusing operators are obtained from the conventional data (focusing operator updating as described in the previous section), and after that the velocity model is estimated by inverting these focusing operators. In the model, both the velocity and the exact locations of the focus points are unknown. The inversion of the focusing operators should result in a velocity model (that represents the velocity structure of the subsurface) and the exact location of the focus points (that corresponds to reflection energy). This inversion process is carried out with traveltime tomography.