First step: The time t0 in a true model is the same as in the example:
Second step: If we apply 15-degree algorithm with the continuation velocity , then discontinuities propagate in accordance to the Eiconal equation
(see equation (98) from Chapter 8 at ).
The solution of this equation which satisfies boundary condition is:
Third step: From the condition we find location of the reflector image
so the depth distortion is very small for subhorizontal reflectors.