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针对起伏地表下的弹性波模拟问题,本文采用高阶交错网格有限差分法剖分网格;在前人的基础上,提出改进型真空法处理起伏地形自由界面:设置一虚拟层于自由界面上,对自由界面的弹性参数取平均;同时,按照参数在交错网格上的安放特点,只需处理剪切应力,并令其值为零;用速度平均法处理速度,把自由界面上方区域内的速度设置为零.本文模拟了几个工程勘探中典型地质模型的炮集记录.结果表明,地表起伏使地震波场复杂化,波型相互转化,产生地表散射,反射波同相轴扭曲、截断甚至淹没,信噪比降低.本文提出的改进型真空法能够确保算法的稳定性和精度,表现出良好的效果.
Aiming at the elastic wave simulation problem under the fluctuating subsurface, this paper adopts the high-order staggered grid finite difference method to mesh the mesh. On the basis of the predecessors, an improved vacuum method is proposed to deal with the undulating terrain free interface: On the free surface of the elastic parameters of the average; the same time, according to the parameters placed in the staggered grid on the characteristics of only dealing with shear stress, and to make its value is zero; speed average method of processing speed, the free area above the interface And the velocity inside is set to zero.This paper simulates the record of cannon-set of several typical geological models in engineering exploration.The results show that the surface undulation complicates the seismic wavefield, and the modes transform into each other, resulting in surface scattering, distorted, Even submerged, the signal to noise ratio is reduced.The improved vacuum method proposed in this paper can ensure the stability and accuracy of the algorithm and show good results.