地震波各向异性走时层析成像有限元模型仿真

Seismic Wave Anisotropy Travel Time Tomography Finite Element Model Simulation

为解决当前地震波各向异性走时层析成像方法中存在的成像准确性差、耗时长的问题,提出基于有限元的地震波各向异性走时层析成像方法。利用地震波应力张量分量、地震波应变张量分量、矢量松弛子函数值分量等参数计算线性粘弹性介质的应力应变关系,并根据所得结果获取地震波各向异性介质本构方程的应力应变之间的关系,完成地震波本构关系的分析。依据分析结果,得到地震波三维各向异性粘弹介质运动方程。基于所得本构关系与运动方程,对地震波应变位移关系进行分析,并得到质量矩阵、阻尼矩阵、刚度矩阵和力矩阵等参量。利用所得参量设置切向边界和法向边界,将地震波各向异性走时有关参数输入至ANSYS软件中的Plane182单元,完成地震波各向异性走时层析成像。实验结果表明,该方法模拟地震波各向异性走时层析成像结果与实际结果拟合程度高,成像耗时短。

In order to solve the low accuracy of image formation in the current seismic anisotropy travel-time tomography method,this paper puts forward a method of anisotropic travel-time tomography method based on finite element.Firstly,the stress-strain relationship of a linear viscoelastic medium was calculated through some parameters such as the stress tensor component of seismic wave,the strain tensor component of seismic wave and the component of phasor relaxation subfunction,and then based on the obtained results,the relationship between stress and strain of constitutive equation of seismic wave anisotropic medium was obtained,so as to complete the analysis of seismic wave constitutive relationship.Based on the analysis result,the motion equation of three-dimensional anisotropic viscoelastic medium of seismic wave was obtained.On the basis of constitutive relation and the motion equation,the strain-displacement relation was analyzed and some parameters such as mass matrix,damping matrix,stiffness matrix and force matrix were obtained.Finally,the obtained parameters were used to set the tangential boundary and the normal boundary.Then,relevant parameters of anisotropy travel time of seismic wave were inputted to Plane182 unit in ANSYS software.Thus,the seismic anisotropy travel-time tomography was completed.Simulation results show that the simulation result of proposed method has high fitting degree with the actual results.Meanwhile,the image formation takes a short time.