Abstract

Multichannel analysis of surface waves (MASW) has received increasing attention in many disciplines in recent years. However, there are still issues with this method, which require further investigation. The most common issues include a potentially poor-resolution experimental dispersion image, near-field effects, and modal misidentification. Therefore, this paper examines the performance of four common wavefield transformation methods for MASW data processing. MASW measurements were performed using Rayleigh and Love waves at sites with different stratigraphy and wavefield conditions. For each site, dispersion curves were generated using the four transformation methods. For sites with a very shallow and highly variable bedrock depth with a high-frequency point of curvature (> 20 Hz), the phase shift (PS) method leads to a very poor-resolution dispersion image for approximately half the experimental datasets compared to other transformation methods. When a velocity reversal was present, the slant stack (τp) method failed to resolve the dispersion image for frequencies associated with layers located below the velocity reversal layer. For sites where multiple modes are present, it was observed that the four transformation techniques have different sensitivities to higher modes. The cylindrical frequency domain beamformer (FDBF-cylindrical) method was determined to be the best method under most site conditions. This method allows for a stable, high-resolution dispersion image for different sites and noise conditions over a wide range of frequencies, and it mitigates the near-field effects by modeling a cylindrical wavefield. Overall, the best practice is to use the composite dispersion approach that combines all transformation methods or at least use two different transformation methods (FDBF-cylindrical and one of the other methods) to enhance the data quality, particularly for complex stratigraphy environments.

Article Highlights

• The FDBF-cylindrical method provides the highest resolution experimental dispersion image compared to the other methods

• The phase shift method sometimes has resolution issues for sites with a very shallow, highly variable bedrock depth with a high-frequency point of curvature

• The best practice is to use the composite dispersion approach or combine at least two transformation methods (FDBF-cylindrical and one of the other methods) to improve data quality, particularly for complex environments

中文翻译：

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考虑各种场地条件、近场效应和模态分离的 MASW 数据处理的不同转换技术的性能

摘要

近年来，表面波多通道分析 (MASW) 在许多学科中受到越来越多的关注。但是，这种方法仍然存在问题，需要进一步研究。最常见的问题包括分辨率可能较差的实验色散图像、近场效应和模式错误识别。因此，本文研究了四种常见的波场变换方法在 MASW 数据处理中的性能。MASW 测量是在具有不同地层和波场条件的地点使用瑞利波和洛夫波进行的。对于每个站点，使用四种转换方法生成分散曲线。对于基岩深度非常浅且高度可变且具有高频曲率点 (> 20 Hz) 的站点，与其他变换方法相比，相移 (PS) 方法导致大约一半的实验数据集的分辨率非常差的色散图像。当存在速度反转时，倾斜叠加 (τp) 方法无法解析与位于速度反转层下方的层相关的频率的色散图像。对于存在多种模式的站点，观察到四种转换技术对更高模式具有不同的敏感性。圆柱形频域波束形成器（FDBF-圆柱形）方法被确定为大多数现场条件下的最佳方法。这种方法可以在很宽的频率范围内为不同地点和噪声条件提供稳定、高分辨率的色散图像，并通过对圆柱波场建模来减轻近场效应。

文章亮点

• 与其他方法相比，FDBF 圆柱方法提供了最高分辨率的实验色散图像

• 对于具有高频曲率点的非常浅、高度可变的基岩深度的站点，相移方法有时会出现分辨率问题

• 最佳实践是使用复合色散方法或结合至少两种变换方法（FDBF 圆柱和其他方法之一）来提高数据质量，特别是对于复杂环境