Full-waveform inversion (FWI) is popularly used to obtain a high-resolution subsurface velocity model. However, it requires either a good initial velocity model or low-frequency data to mitigate the cycle-skipping issue. Reflection-waveform inversion (RWI) uses a migration/demigration process to retrieve a background model that can be used as a good initial velocity in FWI. The drawback of conventional RWI is that it requires the use of least-squares migration, which is often computationally expensive, and it is still prone to cycle skipping at far offsets. To improve the computational efficiency and overcome cycle skipping in the original RWI, we have incorporated it into a recently introduced method called efficient wavefield inversion (EWI) by inverting for the Born-scattered wavefield instead of the wavefield itself. In this case, we use perturbation-related secondary sources in the modified source function. Unlike conventional RWI, the perturbations are calculated naturally as part of the calculation of the scattered wavefield in an efficient way. Because the sources in the reflection-based EWI (REWI) are located in the subsurface, we are able to update the background model along the reflection wavepath. In the background velocity inversion, we calculate the background perturbation by a deconvolution process at each frequency. After obtaining the REWI inverted velocity model, a sequential FWI or EWI is needed to obtain a high-resolution model. We determine the validity of our approach using synthetic data generated from a section of the Sigsbee2A model. To further demonstrate the effectiveness of our approach, we test it on an ocean-bottom cable data set from the North Sea. We find that our methodology leads to improved velocity models as evidenced by flatter angle gathers.

中文翻译：

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基于反射的高效波场反演

全波形反演 (FWI) 广泛用于获得高分辨率的地下速度模型。然而，它需要一个良好的初始速度模型或低频数据来缓解周期跳跃问题。反射波形反演 (RWI) 使用偏移/反偏移过程来检索可用作 FWI 中良好初始速度的背景模型。传统 RWI 的缺点是它需要使用最小二乘迁移，这通常在计算上很昂贵，并且仍然容易在远偏移量处跳周期。为了提高计算效率并克服原始 RWI 中的循环跳跃，我们将其合并到最近引入的称为有效波场反演 (EWI) 的方法中，通过反演波恩散射波场而不是波场本身。在这种情况下，我们在修改后的源函数中使用与扰动相关的二次源。与传统的 RWI 不同，扰动是作为散射波场计算的一部分以一种有效的方式自然计算的。由于基于反射的 EWI (REWI) 中的源位于地下，我们能够沿反射波路径更新背景模型。在背景速度反演中，我们通过每个频率的反卷积过程计算背景扰动。获得REWI反演速度模型后，需要进行序列FWI或EWI来获得高分辨率模型。我们使用从 Sigsbee2A 模型的一部分生成的合成数据来确定我们方法的有效性。为了进一步证明我们方法的有效性，我们在来自北海的海底电缆数据集上对其进行了测试。我们发现我们的方法可以改进速度模型，如更平坦的角度道集所证明的那样。