ABSTRACT Reflection traveltime tomography has been used to describe subsurface velocity structures which, in practice, can be used as a background or initial model for pre‐stack depth migration or full waveform inversion. Conventional reflection traveltime tomography is performed by solving an optimization problem based on a ray‐tracing method. As a result, reflection traveltime tomography requires heavy computational efforts to carry out ray tracing and solve a large matrix equation. In addition, like most data‐domain tomography methods, reflection traveltime tomography depends on initial guesses and suffers from non‐uniqueness and uncertainty of solutions. In this research, we propose a deterministic ray‐based reflection traveltime tomography method by applying seismic interferometry. This method does not suffer from the non‐uniqueness problem and does not require a priori information on subsurface media. By adding a virtual layer (whose properties are known) on top of the real surface and applying convolution‐type interferometry, we approximately determine the stationary points (i.e., incident raypaths in the virtual layer). Then, we generate reflection points for a range of assumed velocities and estimate the velocity by considering the number of reflection points and the traveltime difference between the observed and calculated data. The reflection surface can then be recovered by using the estimated velocity. Once the first target layer is resolved, we can recover the whole media by recursively applying the same method to the lower layers. Numerical examples using surface seismic profile data for homogeneous‐layer (with a low‐velocity layer) and inhomogeneous‐layer models and real field data experiments on the Congo data set demonstrate that our method can successfully recover the velocities and depths of subsurface media without initial guesses. However, our method has some limitations for multi‐layer models because the method does not have sufficient reflection points for the deeper layers.

中文翻译：

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使用近似驻点的基于射线的反射走时层析成像

摘要 反射走时层析成像已被用于描述地下速度结构，在实践中，该结构可用作叠前深度偏移或全波形反演的背景或初始模型。传统的反射走时断层扫描是通过解决基于光线追踪方法的优化问题来执行的。因此，反射走时断层扫描需要大量的计算工作来进行光线追踪和求解大型矩阵方程。此外，与大多数数据域层析成像方法一样，反射走时层析成像依赖于初始猜测，并且存在解的非唯一性和不确定性。在这项研究中，我们通过应用地震干涉测量法提出了一种确定性的基于射线的反射走时层析成像方法。该方法不受非唯一性问题的影响，并且不需要有关地下介质的先验信息。通过在真实表面上添加一个虚拟层（其属性已知）并应用卷积型干涉测量，我们近似确定了静止点（即虚拟层中的入射光线路径）。然后，我们为一系列假定的速度生成反射点，并通过考虑反射点的数量以及观测数据和计算数据之间的走时差来估计速度。然后可以使用估计的速度恢复反射面。一旦解决了第一个目标层，我们就可以通过递归地将相同的方法应用于较低层来恢复整个媒体。使用均质层（具有低速层）和非均质层模型的地表地震剖面数据的数值例子以及刚果数据集上的实场数据实验表明，我们的方法可以成功地恢复地下介质的速度和深度，而无需初始猜测。然而，我们的方法对多层模型有一些局限性，因为该方法没有足够的深层反射点。