一种可模态分离的高分辨率频率-波数法及其工程应用

高分辨率频率-波数法是通过计算F-K谱从能量角度获取主导表面波频散信息的一种常用方法。然而,由于高模态瑞利波的能量通常低于基阶波的能量,因此难以分离多模态频散信息。本文通过建立多模态瑞利波模型,并讨论其相速度、波数和能量特性,提出一种可模态分离的高分辨率频率-波数法。通过增强F-K谱上的高模态能量,提取其多模态能量的局部极值,进而得到相速度点,对所有相速度点进行概率分布并拟合,得到多模态频散曲线。工程应用表明,改进的高分辨率频率-波数法能够较好地还原多模态瑞利波信息,通过对提取的多模态频散曲线进行联合反演,可以得到与工程钻孔结果匹配较好的剪切波速度结构。

A Mode-separable High-resolution Frequency-wavenumber Method and Its Engineering Application

The high-resolution frequency-wavenumber method is a frequently used method to obtain the dispersion information of the dominant surface waves from the perspective of energy by calculating the F-K spectra. However,since the energy of the higher-mode Rayleigh waves is usually lower than that of the fundamental mode,it is often difficult to separate the multi-mode dispersion information. In this paper,an improved high-resolution frequency-wavenumber method for mode separation which establishes a multi-mode Rayleigh waves model is proposed,and its characteristics of phase velocity,wavenumber and energy is discussed. By enhancing the higher-mode energy on the F-K spectra,extracting its local extremums of multi-mode energy to get the phase velocity points,and fitting the probability distribution of all phase velocity points,the multi-mode dispersion curves are extracted. The engineering application shows that the improved method can better restore the information of multi-mode Rayleigh waves,and through the joint inversion of the extracted multi-mode dispersion curves,it is capable to match the shear wave velocity structure with the engineering borehole results.