基于波前最小走时单元的三角网射线追踪全局算法  

A global algorithm of triangular grid ray tracing based on wavefront minimum traveltime unit

作　　者：刘润泽 于师建[2] 田清伟[3] 陆二男 

机构地区：[1]长江工程地球物理勘测武汉有限公司,武汉430010 [2]山东科技大学,青岛266590 [3]中国长江三峡集团公司,宜昌443000

出　　处：《地球物理学进展》2013年第2期1073-1081,共9页Progress in Geophysics

基　　金：国家自然科学基金(50974081);山东省自然科学基金(ZR2011DM014)资助项目

摘　　要：为克服矩形网速度间断面及边界描述精度差的缺点,本文提出了一种基于波前最小走时单元的三角网射线追踪算法.该算法用三角单元剖分速度模型,把与波前面相邻、处于振动状态的三角单元称为波前单元,从源点所在单元开始构造由波前单元组成的波前单元域;1)选域中最小走时三角单元为当前单元;2)它先与相邻三角单元振动传递,再进行相邻单元各自内部节点的传递、并将处于振动状态的相邻单元扩展为波前单元;3)然后确认当前单元的振动状态、决定其在波前单元域中的去留,以此三步循环进行波前单元域的扩展及节点的最小走时和次级源搜索,直至波前单元域在剖分区域的消亡;最后利用各节点最小走时和次级源,通过最小走时搜索,拾取从接收点到源点的射线路径.数值模拟表明,该算法的模型剖分灵活性强,对速度间断面的描述准确,追踪结果精度高.Because of the low accuracy of rectangular grid to describe a velocity interface or a boundary, a triangular grid ray-tracing algoritlhm is proposed based on minimum wavefront traveltime unit. The proposed algorithm splits a velocity model into triangular grid. The unit which is adjacent to the wavefront and under vibration status is defined as wavefront unit. The. wavefront unit zone consisting of wavefront units is constructed from the the source unit. First, select the minimum traveltime triangular unit as the current unit in the wavefront unit zone. Second, the current unit vibrate and transfer to the adjacent triangular units, then transfer between the inner nodes of adjacent unit. the adjacent units which are under the vibration status become wavefront units. Third, the vibration status of the current unit determines whether the current unit stay in the wavefront unit zone or not. Repeating the above three steps of expending the wavefront unit zone and searching for the minimum traveltime and secondary source of nodes, till the wavefront unit zone disappears in the divided region. Finally, using the minimum traveltime and secondary source of each node, we can pick up the ray path from the receive to the source by means of the searching of the minimum traveltime. Numerical results show that our algorithm has high flexibility in model subdivising, high accuracy to describe the velocity interfaces, and high tracing accuracy.

关 键 词：波前最小走时单元 波前单元 波前单元域 波前单元域自动重构 三角网射线追踪 

分 类 号：P631[天文地球—地质矿产勘探]