波前扩展有限差分地震波走时算法的C++语言描述

回顾了波前扩展有限差分地震波走时算法及其主要优缺点，分析了该算法在程序实现过程中存在的一些问题。针对这些问题，给出了波前扩展有限差分地震波走时算法的C⁺⁺语言描述。目的是:（1）确保程序的稳定性。使用体波、首波、散射波相结合的走时算法，在保证走时计算精度的同时，较好地解决了前述算法在局部速度差异较大的情况下可能会出现负数开平方问题；（2）提高程序的执行效率。给出一种波前点的“列队”式存储方法，有效提高了波前最小走时点的查找效率；（3）为波前扩展有限差分地震波走时算法构建一个方便、可行的程序框架。对原始速度模型增加了边界，不仅方便了程序实现，而且省去了程序用于判断和处理模型边界所花费的时间。

An C++ Language Program Implement of Traveltime Calculation of Expanding Wavefronts Finite-Difference Method

We first review the finite-difference scheme proposed by Qin in 1988 which solves the eikonal equation along expanding wavefronts and analyze its advantages and disadvantages.We also show some problems about its programming implement.Then we show an implement method in the C programming language,which aims at solving the problems.(1) To ensure the stability of the program,we also consider the refracted and diffracted waves to calculate the traveltimes.The new method improves the local algorithmic stabilities of Qin's method without losing the precise.(2) To improve the efficiency of the program,we propose a queue storage structure of the wavefront points.(3) We build a convenient and doable program structure for the expanding wavefronts method.We append four boundaries to the original velocity model,which not only makes programming simple but also save the time dealing with the model boundaries.