Abstract:

The wavefront marching methods based on level-sets，such as FMM(fast marching method) and GMM(group marching method) are widely used as an effective scheme of computing the wavefront time in complex media.The precision of traveltime at grid points，calculated with finite-difference solutions of Eikonal equation，is rather low when the sizes of discrete grids are large.In order to improve the precision of wavefront time calculation，a higher accuracy algorithm of wavefront time computation in 3-D inhomogeneous media is presented based on GMM method and Fermat Principle，with traveltime on arbitrary positions represented by bilinear interpolation functions of the known wavefront time on the grid nodes in each cuboid cell.Numerical simulation shows that the method can not only improve the computational accuracy greatly，but also be strong in stability and flexibility in complex media.

Key words: wavefront time, interpolation, wavefront marching, propagation time, finite-difference