ABSTRACT Obtaining high‐quality ground penetrating radar (GPR) images in karst is difficult because materials resulting from the weathering of carbonate rocks might be electrically conductive. As a consequence, penetration depth and signal resolution might be greatly reduced due to attenuation. In addition, fractures and faults might cause a significant amount of electromagnetic wave scattering. We present a 2D data processing flow which allows improving the quality of GPR images in carbonate karst. The processing flow is composed of the following steps: obtaining a zero‐offset section by removing the direct wave, low‐frequency noise removal, geometrical spreading and exponential gain compensation, spectral balancing, Kirchhoff migration, bandpass filtering, amplitude‐volume enhancement, and topographic correction. For a 200‐MHz dataset, we present in detail each step of the processing flow, exemplifying how to parameterize every step. Spectral balancing is of key importance because it can approximately replenish the high‐frequency content lost due to propagation effects. In this step, we recommend to shift the centroid frequency as much as possible to high‐frequency values, even exceeding the nominal value of the antenna center frequency, but still looking for a band‐limited spectrum as the goal. Despite the difficulty of migrating GPR data, we show that migration (even assuming a constant velocity) might enhance the lateral continuity of the reflection events and allows identification of discontinuities such as faults and fractures. If imaged in a better way, these structures can have special importance as they are often the boundaries of dissolution features. Obtaining images based on amplitude‐volume enhancement techniques allows to better visualize karst voids and deep‐rooted discontinuities because these features are often associated with low‐amplitude zones, which are highlighted in such images. Due to this processing flow, stratigraphic, structural and dissolution features can be enhanced, allowing the interpreter to establish spatial and genetic associations among these elements to obtain a better understanding of the karst formation process.

中文翻译：

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通过数据处理增强碳酸盐岩溶地探地雷达图像的地层、构造和溶解特征

摘要 在岩溶中获得高质量的探地雷达 (GPR) 图像很困难，因为碳酸盐岩风化产生的材料可能是导电的。因此，由于衰减，穿透深度和信号分辨率可能会大大降低。此外，裂缝和断层可能会导致大量的电磁波散射。我们提出了一个 2D 数据处理流程，它可以提高碳酸盐岩溶中 GPR 图像的质量。处理流程由以下步骤组成：通过去除直达波、低频噪声去除、几何扩展和指数增益补偿、频谱平衡、基尔霍夫偏移、带通滤波、幅度-体积增强和地形校正。对于 200 MHz 的数据集，我们详细介绍了处理流程的每个步骤，举例说明了如何对每个步骤进行参数化。频谱平衡至关重要，因为它可以大致补充由于传播效应而丢失的高频内容。在此步骤中，我们建议尽可能将质心频率移至高频值，甚至超过天线中心频率的标称值，但仍以寻找带限频谱为目标。尽管迁移 GPR 数据存在困难，但我们表明迁移（即使假设速度恒定）可能会增强反射事件的横向连续性，并允许识别断层和裂缝等不连续性。如果以更好的方式成像，这些结构可能具有特殊的重要性，因为它们通常是溶解特征的边界。基于振幅体积增强技术获取图像可以更好地可视化岩溶空隙和根深蒂固的不连续性，因为这些特征通常与低振幅区域相关联，在此类图像中突出显示。由于这种处理流程，可以增强地层、构造和溶解特征，使解释者能够在这些元素之间建立空间和成因关联，从而更好地了解岩溶形成过程。