A method of three-dimensional ray tracing and model parameterization is presented. The method is intended for propagation media with a
laterally varying velocity and thickness. Developed algorithm in this study (FAIT-3D) is based on the shooting ray tracing technique and solves 3-D
Eikonal equations using finite difference methods. While rays are being traced, the traveltimes and their partial derivatives with respect to
parameters of the model grids are calculated. In order to evaluate the
adequacy and robustness of the algorithm, two synthetic models with several in-line profiles were used. The results surpassed our expectations in
several ways.