In a homogeneous medium, the seismic energy generated by a shot propagates
along the straight rays that connect the shot position *x*_{s}, reflector position
(*x*,*z*), and receiver position *x*_{r}. The total travel-time of this propagation
can be formulated as

(1) |

(2) |

Equations (1) and (2) define the relations between two travel times and are the key equations of kinematic operators for imaging.

1/13/1998