Ray tracing in anisotropic media with a linear gradient

SUMMARY In general, ray paths in anisotropic media can be found by solving the sixth‐order kinematic ray equations. In this paper it is shown that in media where the density‐normalized elastic parameters depend quadratically on one coordinate, i.e. the velocities vary linearly, the projection of the ray path on to the slowness vector plane, which is fixed, is the same shape as the cross‐section of the slowness surface. Thus the ray path can be found by solving a polynomial equation. The deviation of the ray path from the plane and the travel time can be calculated by evaluating a simple integral along the ray.