Full-waveform inversion (FWI) has demonstrated increasing success in estimating medium properties, but its computational cost still poses challenges in moving towards high-resolution imaging of targets at depth. Here, we propose a target-oriented FWI method that inverts for the medium parameters confined within an arbitrary region of interest. Our method is novel in terms of both local wavefield modelling and data redatuming, in order to build a target-oriented objective function which is sensitive to the target medium only without further assumptions about the medium outside. Based on the convolution-type representation theorem, our local forward modelling operator propagates wavefields within the target medium only while providing full acoustic coupling between the target medium and the surrounding geology. A key requirement of our local FWI method is that the subsurface wavefields surrounding and inside the target be as accurate as possible. As such, the subsurface wavefields are retrieved by the Marchenko method, which can redatum the single-sided surface reflection data to the target zone while preserving both primary and multiple reflections, with minimal a priori knowledge of the full-domain medium. Given a sufficiently accurate initial velocity macromodel, our numerical examples show that our local FWI method resolves the reservoir zone of a 2-D Barrett Unconventional P-wave velocity model much more efficiently than the conventional full-domain FWI without significantly sacrificing accuracy. Our method may further enable FWI approaches to high-resolution imaging of subsurface targets.

中文翻译：

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使用Marchenko重推波场的面向目标全波形反演

全波形反演（FWI）在估计介质性质方面已显示出越来越大的成功，但是其计算成本仍然对向深度目标进行高分辨率成像提出了挑战。在这里，我们提出了一种面向目标的FWI方法，该方法可以对限制在任意感兴趣区域内的介质参数进行求逆。我们的方法在局部波场建模和数据重新基准方面都是新颖的，目的是建立仅对目标介质敏感的，面向目标的目标函数，而无需进一步假设外部介质。基于卷积类型表示定理，我们的本地前向建模算子仅在提供目标介质与周围地质之间的全声耦合的同时传播目标介质内的波场。我们本地FWI方法的关键要求是目标周围和内部的地下波场应尽可能准确。这样，地下波场可以通过Marchenko方法进行检索，该方法可以将单面表面反射数据重新映射到目标区域，同时保留一次和多次反射，并且最小化全域媒体的先验知识。给定足够准确的初始速度宏模型，我们的数值示例表明，我们的局部FWI方法比常规的全域FWI更加有效地解析了二维Barrett非常规P波速度模型的储层，而没有显着牺牲精度。我们的方法可能进一步使FWI方法能够对地下目标进行高分辨率成像。