使用表面波的多通道分析从分布式声传感测量中提取高分辨率、多模式表面波频散数据
Extracting High-Resolution, Multi-Mode Surface Wave Dispersion Data from Distributed Acoustic Sensing Measurements using the Multichannel Analysis of Surface Waves
摘要：
我们严格评估的潜力，提取高分辨率，多模式表面波色散数据的分布式声学传感（DAS）测量使用有源多通道分析表面波（MASW）。我们利用高度控制，宽带可控震源振动台车和更多的变量，窄带大锤源激发近地表，并比较DAS派生的分散数据直接从两种源类型与同时获得的传统的检波器派生的分散数据。我们发现，这两种传感方法之间的差异是最小的，以及与每个单独的测量类型的色散不确定性范围内，当满足以下条件DAS：（a）使用紧缓冲或应变传感光纤电缆，（b）电缆埋在浅沟，以提高耦合，（c）短的标距长度和小的通道间隔使用。我们还表明，MASW处理后的频散图像的频率相关归一化消除了测量波形的缩放，积分和微分的影响，从而允许从检波器波形和DAS波形中提取几乎相同的频散数据，而不需要首先将它们转换为等效单位。我们证明了短波长DAS色散测量受到标距和更普遍考虑的通道分离的限制。我们进一步表明，它是可能的提取基本上等效的表面波色散数据从地震测量使用传统的检波器阵列或两个不同的DAS电缆。最后，我们表明，剪切波速度剖面恢复DAS数据使用不确定性一致的，多模式反演同意顺利与锥贯入试验在现场进行。
英文摘要：
We rigorously assess the potential for extracting high-resolution, multi-mode surface wave dispersion data from distributed acoustic sensing (DAS) measurements using active-source multichannel analysis of surface waves (MASW). We have utilized both highly-controlled, broadband vibroseis shaker trucks and more-variable, narrow-band sledgehammer sources to excite the near surface, and compare the DAS-derived dispersion data obtained from both source types directly with concurrently acquired traditional geophone-derived dispersion data. We find that the differences between the two sensing approaches are minimal and well within the dispersion uncertainty bounds associated with each individual measurement type when the following conditions are met for DAS: (a) a tight-buffered or strain-sensing fiber-optic cable is used, (b) the cable is buried in a shallow trench to enhance coupling, and (c) short gauge lengths and small channel separations are used. We also show that frequency-dependent normalization of the dispersion image following MASW processing removes the effects of scaling, integration, and differentiation on the measured waveforms, thereby allowing nearly identical dispersion data to be extracted from geophone waveforms and DAS waveforms without requiring them to first be converted into equivalent units. We demonstrate that the short wavelength DAS dispersion measurements are limited by both the gauge length and the more commonly considered channel separation. We further show that it is possible to extract essentially equivalent surface wave dispersion data from seismic measurements made using a traditional geophone array or two different DAS cables. Finally, we show that shear wave velocity profiles recovered from the DAS data using an uncertainty-consistent, multi-mode inversion agree favorably with cone penetration tests performed at the site.
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