三维层状介质中基于走时梯度的多次波射线追踪  

Multiple ray tracing in 3D layered media using the traveltime gradient method

作　　者：张婷婷[1,2] 张东[1] 邱达[2] 

机构地区：[1]武汉大学物理科学与技术学院,湖北武汉430072 [2]湖北民族学院信息工程学院,湖北恩施445000

出　　处：《石油地球物理勘探》2014年第6期1097-1105,3,共9页Oil Geophysical Prospecting

基　　金：国家科技重大专项(2008ZX05020-006)资助

摘　　要：本文结合分区多步思想改进初至波走时梯度射线追踪算法(MTG),使之能适用于三维层状介质中多次波射线追踪计算。在计算过程中按照射线类型和速度分界面将三维模型分为不同的计算区域,根据多次波的传播顺序从震源开始在对应的区域内采用网格剖分线性插值法计算波前走时场。然后从检波点开始根据多次波的类型在对应的计算区域内沿走时梯度方向分步追踪多次波射线路径。在计算多次波波前走时场的过程中,为提高计算效率加入了逐次网格剖分技术,使分界面上波前新的震源位置更加精确;在多次波射线追踪的过程中根据走时梯度方向追踪射线路径,在速度分界面区域内采用局部追踪策略求取下一个追踪点以提高多次波的射线精度。本文在多层层状介质模型及扩展到三维的Marmousi模型中进行试验,计算结果表明,改进的MTG算法结合分区多步技术计算多次波时具有常规MTG法计算初至波时的优点,计算精度高、算法简单、计算效率高,验证了MTG算法在复杂的三维模型中计算多次波的有效性。The purpose of this paper is to present a multistage maximum taveltime gradient ray tracing method(MTG)for tracing multiple seismic arrivals in a 3Dlayer media.First a reflected or refracted wavefront can be calculated in the order of the multiple transmissions by partitioning layers intoseparate computational domains in which the dynamic successive partitioning scheme is applied.The next step is to track the multiple arrivals along the negative traveltime gradient using the traveltime information we have obtained.The successive partitioning of cell interfaces is used to improve the efficiency of the multiple wavefront traveltime field calculation,hence,we can find a more accurate secondary source point with a minimum traveltime.The multiply-arriving ray path can be traced from the receiver to the source along the negative traveltime gradient.In the area of velocity interface we adopted a local ray tracing strategy to improve the precision of multiply arrival ray paths.Several examples(including 3D Marmousi model and layered media)and error analysis indicate that the multistage MTG method retains the basic characteristics of the first arrival MTG method with high computational accuracy,algorithm simplicity,and numerical stability,and the result demonstrate the viability of the multistage MTG in heterogeneous media.

关 键 词：多次波追踪 分区多步 走时梯度算法 线性插值 

分 类 号：P631[天文地球—地质矿产勘探]