求解三维程函方程的波前扩展法

SOLUTION OF 3-D EIKONAL EQUATION BY EXPANDED WAVEFRONT METHOD

Vidale used the finite difference method in solving 3-D eikonal equation. Such method will however violate the causal law in case of large velocity variations. Qin's 2-D general wavefront expansion theory is capable of tackling the problem in vidalc's method, it is thus used here to get an improved solution for the 3-D eikonal equation. The traveltimes calculated by the improved method arc the first arrival times in the absolute sense. The procedure for calculating traveltimes of reflected and converted waves is also involved in this paper without any approximation on the 3-D eikonal equation. The computational results show that the method is practicable and accurate even in case of large velocity variation.