Joint Inversion of VTI Parameters Using Nonlinear Traveltime Tomography

In this paper, we use a nonlinear tomographic method to jointly invert the multiple parameters in VTI media. It is based on the harmonic series of group velocity to calculate the Fréchet kernels of traveltime respect to model parameters. Two parameterizations are used. Through theoretically analysis and numerical experiments, we find that the parameterization of vertical slowness, horizontal slowness, and NMO slowness is more appropriate for joint traveltime tomography, compared with the original Thomsen parameterization. To overcome the physical weak influence of epsilon on traveltime, a double-round strategy is employed in double-parameter inversion, through which epsilon as well as vertical velocity is successfully obtained. The extension from double-round to triple-round strategy also shows great potential to invert all of the three parameters.