提高规则网格最短路径方法反射波走时计算精度的走时校正技术  

A traveltime correction technique for improving the accuracy of reflection wave traveltimes with the shortest path method based on a regular grid

作　　者：赵爱华[1] 徐涛[2] 

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029

出　　处：《地球物理学进展》2012年第5期1854-1862,共9页Progress in Geophysics

基　　金：国家自然科学基金项目(40974050;40674044;41174075);中央国家级公益事业单位基本科研业务费重大计划专项(DQJB11C03)资助

摘　　要：最短路径射线追踪方法是计算地震波走时的主要方法之一,该方法基于惠更斯原理和费玛原理,具有稳健、适于复杂介质模型的优点.为处理方便,最短路径方法中的介质模型通常以规则网格进行剖分,界面节点(界面与网格的交点)以其邻近的模型单元节点(即边界单元节点)近似表示.界面近似将导致计算误差,对于反射波尤为严重.反射波的走时精度可通过减小网格的尺寸提高,但这样会大大增加计算时间.为高精度和高效率地计算地震反射波走时,我们提出了一种基于规则网格的走时校正技术.地震波传播至或起始于边界单元节点的走时校正为地震波传播至或起始于该边界单元节点所对应的界面节点的走时.数值模型计算结果表明,走时校正方法可使反射波的走时精度提高约1～2个数量级,而其计算时间则和常规算法基本上在相同量级.The shortest path method is one of main approaches of calculating seismic traveltimes.The ray tracing method is based on Huygens＇ and Fermat＇s principles,and can be applied to complex velocity models due to its excellent robustness.For convenience,the velocity model is usually divided into small equal elements with a regular grid,taking the points at the centers of the elements as model nodes.Accordingly,an interface node,namely an intersection point of an interface with the model node grid,is approximately represented with its adjacent model node,which is referred to as a boundary model node.The interface approximation certainly produces traveltime errors,which is accentuated for reflection waves.The traveltime error can be reduced by decreasing the model element size,at the large cost of computation time.For efficiently calculating reflection wave traveltime with high accuracy,we put forward a traveltime correction technology which is combined with the shortest path method based on a regular grid.The traveltime of a secondary wave from or to a boundary model note is corrected to that of the wave from or to the corresponding interface node.Numerical examples show that by employing the traveltime correction technology,the traveltime accuracy of reflection waves can be improved by about 1~2 orders of magnitude while the computational time maintains the same magnitude order as that of the normal algorithm.

关 键 词：反射波 射线追踪 最短路径方法 规则网格 走时校正 

分 类 号：P315[天文地球—地震学]