Reconstructing the details of subsurface structures deep beneath complex overburden structures, such as subsalt, remains a challenge for seismic imaging. Over the past few years, the Marchenko redatuming approach has proven to reliably retrieve full-wavefield information in the presence of complex overburden effects. When used for redatuming, current practical Marchenko schemes cannot make use of a priori subsurface models with sharp contrasts because of their requirements regarding initial focusing functions, which for sufficiently complex media can result in redatumed fields with significant waveform inaccuracies. Using a scattering framework, we evaluate an alternative form of the Marchenko representation that aims at retrieving only the unknown perturbations to focusing functions and redatumed fields. From this framework, we have developed a two-step practical focusing-based redatuming scheme that first solves an inverse problem for the background focusing functions, which are then used to estimate the perturbations to focusing functions and redatumed fields. In our scheme, initial focusing functions are significantly different from previous approaches because they contain complex waveforms encoding the full transmission response of the a priori model. Our goal is the handling of not only highly complex media but also realistic data — band-limited, unevenly sampled, free-surface-multiple contaminated data. To that end, we combine the versatility of Rayleigh-Marchenko redatuming with our scattering-based scheme allowing an extended version of the method able to handle single-sided band-limited multicomponent data. This scattering-Rayleigh-Marchenko strategy accurately retrieves wavefields while requiring minimum preprocessing of the data. In support of the new methods, we evaluate a comprehensive set of numerical tests using a complex 2D subsalt model. Our numerical results indicate that the scattering approaches retrieve accurate redatumed fields that appropriately account for the complexity of the a priori model. We find that the improvements in wavefield retrieval translate into measurable improvements in our subsalt images.

中文翻译：

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基于散射的聚焦，用于从带宽受限的多分量数据在高度复杂的介质中成像

重建复杂上覆结构（如盐下）深处的地下结构细节仍然是地震成像的挑战。在过去几年中，Marchenko 重定标方法已被证明可以在存在复杂覆盖层效应的情况下可靠地检索全波场信息。当用于重定标时，当前实用的 Marchenko 方案不能使用具有鲜明对比的先验地下模型，因为它们对初始聚焦函数的要求，对于足够复杂的介质，这可能导致重定标场具有明显的波形不准确度。使用散射框架，我们评估了 Marchenko 表示的另一种形式，该形式旨在仅检索聚焦函数和重新校准场的未知扰动。从这个框架来看，我们开发了一个两步实用的基于聚焦的重定标方案，首先解决背景聚焦函数的逆问题，然后用于估计聚焦函数和重定标场的扰动。在我们的方案中，初始聚焦函数与以前的方法有很大不同，因为它们包含编码先验模型的完整传输响应的复杂波形。我们的目标不仅是处理高度复杂的媒体，还包括现实数据——带限、不均匀采样、自由表面多重污染的数据。为此，我们将 Rayleigh-Marchenko 重定标的多功能性与我们基于散射的方案相结合，允许该方法的扩展版本能够处理单边带限多分量数据。这种散射-Rayleigh-Marchenko 策略可以准确地检索波场，同时需要对数据进行最少的预处理。为了支持新方法，我们使用复杂的 2D 盐下模型评估了一组综合数值测试。我们的数值结果表明，散射方法可以检索准确的标定场，这些场适当地说明了先验模型的复杂性。我们发现波场检索的改进转化为我们盐下图像的可测量改进。我们的数值结果表明，散射方法可以检索准确的标定场，这些场适当地说明了先验模型的复杂性。我们发现波场检索的改进转化为我们盐下图像的可测量改进。我们的数值结果表明，散射方法可以检索准确的标定场，这些场适当地说明了先验模型的复杂性。我们发现波场检索的改进转化为我们盐下图像的可测量改进。