Multiple ray tracing in 2D layered media with the shortest path method

The purpose of this study aims at introducing the multistage scheme incorporating with a modified shortestpath method (MSPM)for tracking multiple arrivals and simulating wavefront evolutions composed of any kind of combinations of transmissions,conversions and reflections in 2D layered media.The principle is first to divide the layered model into several different computational domains,and then to use the multistage technique to trace the multiple arrivals.It is possible to realize the multiple arrival tracking with the multistage technique because the multiple arrivals are the different combinations of the simple incident,transmitted,reflected and converted waves via velocity boundaries (or discontinuities).By treating each separate layer that the wavefront enters as an independent computational domain,one can simulate wavefront transmission and mode conversion by reinitializing it in the adjacent layer,and wavefront reflection (and/or conversion)by reinitializing it in the incident layer.Numerical tests and error analysis indicate that the multistage MSPM method retains the basic characteristics of the single-stage MSPM approach,that is algorithm simplex,numerical stability,high computational accuracy,fast,global solution and etc. Therefore it is a practical algorithm for tracking multiple arrivals.