三维正交各向异性孔隙介质震电波场数值模拟研究

各向异性等介质物性参数会对震电波场的传播产生影响.为了定量研究介质物性参数对震电波场传播的影响, 本文首先研究了三维正交各向异性介质的震电耦合方程, 然后采用时域有限差分方法模拟了爆炸源在该介质中的震电响应.在数值模拟中, 首先计算地震波场, 然后把地震波场作为输入来计算伴随电场.为了验证数值算法的精度, 我们将数值结果与从Pride方程获得的解析解进行了对比, 结果表明数值解可以很好地近似解析解.
我们设计了几种各向异性模型, 分析了介质物性参数对震电波场的影响, 结果表明爆炸源在各向异性孔隙介质中会产生四种地震波, 分别是快慢纵波和两个可分离的横波.产生的地震波都会在均匀各向异性孔隙介质中产生伴随电场.弯曲度对慢纵波的传播有影响, 当弯曲度为各向异性时, 慢纵波的波场快照为椭圆形, 当弯曲度为各向同性时, 慢纵波的波场快照为圆形.

Numerical simulation of seismoelectric wavefields in 3D orthorhombic poroelastic medium

The anisotropy and other medium parameters have influences on the propagation of seismoelectric wavefields. With the aim of quantitatively analyzing the effects of medium parameters on seismoelectric wavefields, we firstly studied the seismoelectric coupling equations in 3D orthorhombic poroelastic medium, and then computed the seismoelectric responses by time domain finite-difference algorithm with an explosive source. In numerical simulation, we firstly simulated the seismic wavefields, and then used seismic wavefields as input to compute electric wavefields. We compared the numerical results with analytical results obtained from Pride equations to test the algorithm and find that the analytical solution is well approximated by numerical solution. We designed several anisotropic models and analyzed the influence of medium parameters on the seismoelectric wavefields.
Numerical results show that the explosive source generates four types of seismic waves in anisotropic porous medium, which are two separable transverse waves and the fast and slow longitudinal waves. All seismic waves were accompanied by coseismic electric wavefields in homogeneous anisotropic porous medium. The tortuosity has an influence on the propagation of slow longitudinal waves. The wavefield snapshot of slow longitudinal wave has an oval shape when the tortuosity is anisotropic, while it has a circular shape when the tortuosity is isotropic.