地震波旅行时计算方法及其模型试验分析

Computation method for seismic wave travel-time and its model experiment analysis

地震波旅行时的计算是地震波偏移成像技术和地震层析成像技术的核心内容,同时也是实现保幅叠前偏移成像的重要因素。推导了地震波波动方程高阶有限差分法计算格式,提出了最大绝对振幅能量节点初至旅行时拾取的方法。均匀介质模型试验表明,该方法与用解析解、程函方程法计算的旅行时等值线基本重合。基于层状介质模型、凹陷模型和Marmousi模型对方法的适用性进行了试验,将由该方法计算得到的初至旅行时作为叠前逆时成像条件,对凹陷模型和Marmousi模型的数值模拟记录进行了叠前逆时偏移成像,偏移叠加剖面很好地反映了模型的地质特征。

The computation of seismic wave travel-time is the core for seismic wave migration and seismic tomography,which is also an important factor for realizing amplitude-preservation pre-stack migration. We derived the high-order finite-difference computational format for seismic wave equation,and put forward to a method for picking up first arrival corresponding to maximal absolute amplitude energy while forward modeling.The experiment on the isotropic model shows that the contour maps of travel-time obtained by our method are almost overlapped with that of analytical method and eikonal equation method.The applicability of the method was tested on layered medium model,depression model and Marmousi model,what's more,the first-arrival travel-time calculated by our method was taken as the imaging condition to carry out pre-stack reverse-time migration on the numerical simulated records of depression model and Marmousi model.The migration and stack sections perfectly reflect the geologic characteristics of the models.