Rayleigh wave three-component beamforming: signed ellipticity assessment from high-resolution frequency-wavenumber processing of ambient vibration arrays
Rayleigh wave three-component beamforming: signed ellipticity assessment from high-resolution frequency-wavenumber processing of ambient vibration arrays
复制标题
瑞利波三分量波束形成：根据环境振动阵列的高分辨率频率波数处理进行有符号椭圆度评估
DOI：
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发表时间：
2018
影响因子：
2.8
通讯作者：
M. Ohrnberger
中科院分区：
文献类型：
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作者：
M. Wathelet;Bertrand Guillier;Philippe Roux;Cécile Cornou;M. Ohrnberger
李晓明，李晓明，李晓明，等。瑞利椭圆率随频率的变化在场地表征中越来越受欢迎。在反演横波速度剖面时，它成为补充频散曲线的必要观测值。到目前为止，已经提出了各种方法来从单个三分量站或三分量传感器阵列记录的环境振动中提取偏振。如果只在10年前恢复绝对值，那么最近提出的基于阵列的新技术具有提高的效率，同时提供椭圆性符号。通过阵列处理，即使在椭圆域也可以检测到高阶模。我们建议探索高分辨率波束形成的特性，其中明确包括径向和垂直分量。如果N是三分量传感器的数目，则计算所有假定传播方向的2N × 2N交叉光谱密度矩阵。它们有N个径向通道和N个垂直通道。作为第一种方法，转向矢量被设计成适合瑞利波的特性：径向分量和垂直分量之间的相移为- /2或/2。我们表明，忽略衰减引起的椭圆度倾斜对结果的影响很小。此外，我们还分析证明了从通常的高分辨率光束功率最大化中提取椭圆度值是可能的。在合成数据集和实验数据上对该方法进行了测试。它们都是一些作者已经分析过的参考站点。并与以往的研究结果作了详细的比较。
S U M M A R Y The variation of Rayleigh ellipticity versus frequency is gaining popularity in site characterization. It becomes a necessary observable to complement dispersion curves when inverting shear wave velocity profiles. Various methods have been proposed so far to extract polarization from ambient vibrations recorded on a single three-component station or with an array of three-component sensors. If only absolute values were recovered 10 yr ago, new array-based techniques were recently proposed with enhanced efficiencies providing also the ellipticity sign. With array processing, higher-order modes are often detected even in the ellipticity domain. We suggest to explore the properties of a high-resolution beamforming where radial and vertical components are explicitly included. If N is the number of three-component sensors, 2N × 2N cross-spectral density matrices are calculated for all presumed directions of propagation. They are built with N radial and N vertical channels. As a first approach, steering vectors are designed to fit with Rayleigh wave properties: the phase shift between radial and vertical components is either − /2 or /2. We show that neglecting the ellipticity tilt due to attenuation has only minor effects on the results. Additionally, we prove analytically that it is possible to retrieve the ellipticity value from the usual maximization of the high-resolution beam power. The method is tested on synthetic data sets and on experimental data. Both are reference sites already analysed by several authors. A detailed comparison with previous results on these cases is provided.