横向各向同性介质中弹性波模拟及波场特征研究

Elastic wave simulation and the wave field character study in azimuthal isotropic medium

某些结晶或含有裂隙的介质表现出与弹性波传播有关的各向异性。这一性质可以用弹性波动理论建立的质点运动方程和应力应变本构方程（即广义虎克定律）来描述。本文利用傅里叶数值方法（即伪谱法）求解该方程来模拟各向异性介质中弹性议的传播。文中建立了一套模拟算法，研究了各向异性与各向同性介质中弹性波场的特征。发现在某种条件下各向异性介质中qS波波前会产生分叉的所谓三倍效应，并讨论了产生这一效应的约束条件。在裂隙引起的介质各向异性的模拟中，发现qSs型波指示裂隙充液与否可能比qP型波更有效。

Some crystallized or fractured media show anisotropy relating to elastic wave propagation. This character can be escribed by both particle motion equation and stress-strain constitutive equation (i- e. the generalized Hooke's law ) which are de-rived from elastic wave theory. Elastic wave propagation in anisotropic medium is simulated by solving the equation system with the aid' of Fourier numerical method (pseudo-spectrum method). We offer the simulation algorithm, and analyse the characters of elastic wave fields in anisotropic medium and isotropic medium respec-tively. It is found that under some conditions, qS wave front in anisotropic medium often branches, which is called 'the effect of three times'. We aIso discuss the re-straint condition under which the effect occurs. In simulating the medium anisotropy due to fractures, we can find that qS wave may be more effective than qP wave in indicating whether fractures are filled with fluid.Keywords: medium, isotropy, nisotropy, elastic wave, numerical simula-tion, wave field character