ABSTRACT The use of surface wave testing for near‐surface engineering applications has increased in recent years. Typical surface wave analysis is based on the dispersion of surface waves in one‐dimensional layered models. One‐dimensional models are inappropriate for measurements at sites with appreciable lateral variability, a likely scenario in many engineering applications. Use of such models can subsequently undermine the reliability and accuracy of the surface wave results. Full waveform inversion (FWI) is a high‐resolution imaging technique that is proven to outperform the conventional dispersion‐based analysis of surface waves. Much of the near‐surface literature has focused on full waveform inversion of Rayleigh waves developed by the interaction of primary‐ and vertically polarized shear waves (P‐SV), and the capabilities of surface waves generated by horizontally polarized shear waves (Love waves) in mapping near‐surface spatial variabilities have not been fully explored. In this numerical study, full waveform inversion of Rayleigh and Love waves was performed on two different spatially correlated Gaussian random fields (mean VS of 200 and 500 m/s) to mimic the natural spatial variability of geologic materials. Each soil structure was produced at a low and high level of stiffness variability. Two sources with different frequency contents, 25 and 50 Hz, were used to evaluate the effects of source characteristics on the resolution of Rayleigh and Love waveform inversions. The inverted results from the high‐velocity domain demonstrated that Love waveform inversion using high‐frequency seismic sources outperforms Rayleigh full waveform inversion in detecting the shape and the velocities of horizontally deposited geologic materials. Results from the low‐velocity domain also confirmed that Love full waveform inversion was comparable or superior to Rayleigh full waveform inversion, though the performance difference was less significant. However, the 25‐Hz frequency inversions yielded superior results than the 50‐Hz frequency inversions for the low‐velocity domain because the dominant wavelength of the high‐frequency signals becomes so small that it offers an impractically small investigation depth.

中文翻译：

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瑞利和洛夫全波形反演在表征近地表工程应用中土壤空间变异性方面的数值比较

摘要 近年来，表面波测试在近地表工程应用中的使用有所增加。典型的表面波分析基于表面波在一维分层模型中的色散。一维模型不适用于具有明显横向可变性的站点的测量，这是许多工程应用中的一种可能情况。使用此类模型随后会破坏表面波结果的可靠性和准确性。全波形反演 (FWI) 是一种高分辨率成像技术，已被证明优于传统的基于色散的表面波分析。许多近地表文献都集中在由初级和垂直极化横波 (P-SV) 相互作用产生的瑞利波的全波形反演上，水平极化剪切波（洛夫波）产生的表面波在映射近地表空间变化方面的能力尚未得到充分探索。在这项数值研究中，瑞利波和洛夫波的全波形反演在两个不同的空间相关高斯随机场（平均 VS 为 200 和 500 m/s）上进行，以模拟地质材料的自然空间变化。每个土壤结构都是在低和高水平的刚度可变性下产生的。具有不同频率内容的两个源，25 和 50 Hz，被用来评估源特性对瑞利和洛夫波形反演分辨率的影响。高速域的反演结果表明，使用高频震源的Love波形反演在检测水平沉积地质材料的形状和速度方面优于瑞利全波形反演。低速域的结果也证实了 Love 全波形反演与 Rayleigh 全波形反演相当或优于 Rayleigh 全波形反演，但性能差异不那么显着。然而，对于低速域，25Hz 频率反演比 50Hz 频率反演产生了更好的结果，因为高频信号的主波长变得如此之小，以至于它提供了一个不切实际的小调查深度。低速域的结果也证实了 Love 全波形反演与 Rayleigh 全波形反演相当或优于 Rayleigh 全波形反演，但性能差异不那么显着。然而，对于低速域，25Hz 频率反演比 50Hz 频率反演产生了更好的结果，因为高频信号的主波长变得如此之小，以至于它提供了一个不切实际的小调查深度。低速域的结果也证实了 Love 全波形反演与 Rayleigh 全波形反演相当或优于 Rayleigh 全波形反演，但性能差异不那么显着。然而，对于低速域，25Hz 频率反演比 50Hz 频率反演产生了更好的结果，因为高频信号的主波长变得如此之小，以至于它提供了一个不切实际的小调查深度。