一种用于走时层析成像的改进算法

An Improved Algorithm for Travel Time Tomopraphy

走时层析成像是根据首波走时重建声波、地震波或电磁波波速的层析技术，其所用到的射线路径依赖于波速分布．本文提出了一个依据费马原理寻找射线路径的新方法．费马原理指出，从发射点到接点的射线首波的走时极小，因此寻找射线路径的问题是一个最优化问题。我们用加权有向图中寻找最短路经的思想来解决，然后将所得到的射线路径用于一个迭代重建算法中．模拟结果证明该重建算法优于传统的算法，并且稳定性很好．

Traveltime tomography is a technique to reconstruct acoustic, seismic, orelectromagnetic wave-speed distributions from first arrival traveltime data. The my paths thatshould be used for tomographic techniques strongly depend on the wave-speed distribution. Inthis paper, a new method is proposed for finding out the ray paths by using Fermat's prindple, that means the traveltime of the ray path should be a minimum value. The problem offinding out the ray path is actually an optdrium problem. Our new method uses the idea to findout the shortest path in a weighted directed graph to solve this problem. The my paths found out by this method are used in the iterative reconstruction procedure. Computer simulation results produced by this reconstruction algorithm are better than that by the conventional ones. It also shows that the new algorithm is effective with good convergence and stability.