Complex Media-based Shortest Path Ray Tracing Tomography Forward

Seismic tomography is a leading method for reconstructing velocity distribution of the media underground or in cross-hole region, which using the travel-times observed on the surface or in cross-holes. Ray-based tomography, which needs iterated operation of seismic ray tracing forward modeling, is one major method of seismic tomography. As improving the precision and speed of seismic ray tracing algorithm, the precision and speed of the inversion are advanced. This paper studies tomography forward modeling method using the shortest path ray tracing algorithm, SPRT, based on complex media. A program for SPRT algorithm is workout and some models are modeled. The main researching contexts are as follows:In the SPRT algorithm of 2-D geological model, we study two mathematical models with rectangle parameterization and the regularities of nodes' distribution. The process of SPRT forward modeling is discussed particularly.Deduce the equations of wavefront and raypaths in a continuous velocity medium with vertical velocity gradients.Based on the existent SPRT forward modeling methods, we use dense network and large effective radius to improve the precision of SPRT forward modeling. Then, the algorithm speed is discussed.After researching the key problem in SPRT forward modeling for 2-D and 3-D geologic models, some models are modeled.The SPRT forward modeling method with improved measures is discussed in the end.We apply above methods, respectively, to synthetic and real data, and the results show that our methods are valid and effective.