基于旅行时线性插值的地震射线追踪算法

Seismic ray tracing algorithm based on the Iinear traveltime interpolation

本文介绍并实现了一种由Asakawa提出的基于旅行时线性插值的地震射线追踪算法（简称LTI算法），并在此基础上提出了反射波LTI算法。LTI算法基于网格单元模型，适用于任意变速介质，可以追踪包括直达波、折射波、透射波等多种射线路径。原LTI算法处理初至类型的地震波，而本文将其推广到反射波情况，使其可以应用于计算地震反射波的旅行时及追踪反射波射线路径。通过计算试验及与物理模型实验结果对比表明，用该算法计算旅行时和追踪射线路径比其它常规方法（如有限差分法）更为精确，更加适应速度变化大等复杂条件，这是一种很有发展前途的地震射线追踪算法。

In the paper, we introduce and implement a seismic ray tracing algorithm based on the linear travel-time interpolation put forward by Asakawa (called LTI algorithm for short). On the basis of these, the reflected wave LTI algorithm is proposed. The LTI algorithm is based on grid unit model, is adapted to arbitrary variable velocity media, and can be used to trace several kinds of raypaths such as direct wave,refracted wave and transmitted wave. The original LTI algorithm can process the first arrival type of seismic wave. In the paper, we spread it to the refected wave circumstances, making it usable to calcu-late the traveltimes of seismic reflected wave and trace the reflected wave raypaths. The comparison be-tween the calculation and physical model experiment results demonstrates that the algorithm is more pre-cise and more suitable to complicated conditions such as large velocity variation in calculating traveltimes and tracing raypath than other conventional methods (e. g. the finite-difference method). This kind of seismic ray tracing algorithm has a good prospect.