TI介质地震波场数值模拟边界条件处理

Treatment of the boundary conditions in the numerical simulation of the seismic wave field in transversely isotropic(TI) medium

地震波场数值模拟研究中,边界条件处理非常重要,它直接影响模拟地震数据的精度.针对TI(Transversely Isotropic)介质一阶速度—应力弹性波动方程组,利用时间域分裂法给出了PML(Perfectly matched layer,完全匹配层)吸收边界条件,其基本思想是在所研究的区域外引入吸收层,地震波从有效计算区域传播到吸收层时不发生任何反射,且在吸收层内按传播距离呈指数衰减,不发生反射.利用交错网格高阶差分技术对PML吸收边界条件求解,对比不同边界条件数值模拟结果表明,PML吸收边界条件较应用广泛的Clayton吸收边界有更好的吸收效果,能更好地满足地震数值模拟的需要.

The treatment of the boundary condition in the numerical simulation of seismic wave field will directly influence the simulation precision of the seismic data.The perfectly matched layer absorbing boundary conditions of the one-order velocity——stress elastic wave equation in TI medium are derived by using time-domain splitting method.The seismic wave does not reflect when it transmits from effective computation region to absorbing layer,and it exponentially attenuates with spreading distance in the absorbing layer.The numerical simulation results of the perfectly matched layer absorbing boundary conditions and the Clayton absorbing boundary conditions widely applied at present are compared,and it is shown that the absorbing result of the former is better than that of the latter.