Traveltime Inversion: Combination of Reflection Tomography, Migration and Dix Type Approch

In this work we propose a scheme for the kinematic inversion of seismic records by using traveItimes of reflected waves. The ma.cromodel compressional velocity distribution is determined by reflection tomography using nonzero offset tra.veltimes. The structure of the medium is given by depth migration using zero offset travel times which we asaume to correspond to normal incidence rays. An initial guess is given by the Dix type approach and the data are collected from real seismograms by using a Chernyakov's procedure for travel times picking. We consider two types of medium parametrization: triangular cells (local), where the quadratic slowness is a gradient constant function, for ray tracing; and B-splines (global), through Schoenberg's variation diminishing spline approximation, for inversion. In the context of reflection tomography, we obtain analytic derivatives of the traveltime with respect to the medium parameters .and we chose a penalty function combining the nonzero offset traveltime errors and smoothness requirement through second derivative constraint. By selecting convenient spline knots and regularization factors, we obtain unique and stable results.