We consider the partial derivatives of travel time with respect to both spatial coordinates and perturbation parameters. We derive the explicit equations for transforming these travel-time derivatives of arbitrary orders at a general smooth interface between two general media.
The equations are applicable to both real-valued and complex-valued travel time. The equations are expressed in terms of a general Hamiltonian function and are applicable to the transformation of travel-time derivatives in both isotropic and anisotropic media.
The interface is specified by an implicit equation. No local coordinates are needed for the transformation.