Direct Nonlinear Traveltime Inversion in Layered VTI Media

We present a scheme for direct nonlinear inversion of picked moveout traveltimes in block-layered isotropic or VTI media. Using constant ray parameter traveltime differences between successive events allows inversion for velocity parameters of individual layers with no need for explicit layer stripping. We derive explicit closed-form inversion equations that allow this scheme to be implemented as a direct nonlinear method, rather than requiring iterative linearization. The method honors both anisotropy and ray bending effects more accurately than most conventional velocity analysis techniques.