黏弹性EDA介质中地震波的衰减特性研究

本文首先由Christoffel方程推导出黏弹性EDA介质中均匀、 非均匀P波、 SV波和SH波的相速度表达式， 然后参照极端各向异性介质的相关计算方法， 推导出EDA介质中均匀、 非均匀地震波相衰减系数和群衰减系数的表达式， 并通过数值计算分析了相速度、 相衰减系数、 群衰减系数与裂隙方位的关系. 结果表明: 均匀介质中SH波的相速度和相衰减系数均可指示裂隙的走向； 非均匀介质中SH波相衰减系数随非均匀角的增大而增大， 且其对称轴与介质对称轴的夹角也相应增加； 由于地震波振幅的衰减随岩石物理性质的变化比地震波速度的变化更为灵敏, 而且携带了更多的岩石物理性质信息， 因此可用来探明裂隙走向、 密度及含水特性， 进而应用于预测、 预防地下工程地质灾害事故. 

Attenuation characteristics of seismic wave in viscoelastic EDA media

In this paper, the expressions of phase velocities for homogeneous and inhomogeneous P, SV, SH plane waves are derived from Christoffel equation. Phase attenuation coefficient and group attenuation coefficient for inhomogeneous and homogeneous plane wave are derived by the method used for extreme anisotropic medium. The relation between phase attenuation coefficient, group attenuation coefficient and azimuth of cracks is studied through numerical calculation. It is concluded that fracture can be indicative by SH wave phase velocity and attenuation coefficient in a homogeneous medium. SH wave attenuation coefficient increases with the increase of inhomogeneous angle, and the angle between its axis of symmetry and the symmetry axis of media also increases correspondingly in inhomogeneous medium; attenuation of seismic wave amplitude is more sensitive to variation of the rock’s physical properties than the variation of wave velocity, and it carries more information about petrophysical properties. Therefore, it can be used to probe the azimuth of cracks, crack density, water content and to forecast and prevent from geological disasters in underground engineering.