【摘要】 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.更多还原

【Abstract】 In this paper,for the problem of elastic wave simulation in the condition of rugged surface,a high-order staggered finitedifference method is used in grid subdivision; Based on the existing works,the improved vacuum method is put forward to handle the free interface of undularing topography in this paper. A virtual layer is set up on the free interface,and the elastic parameters are set to be average numbers. Meanwhile,according to the characteristics of parameters in the staggered grid,only the shear stress needs to be handled,and its value is zero. The velocity is dealt by velocity average method,the velocity above the free interface is set to be zero. In this paper,several typical shot gathers record of geological models in engineering exploring are simulated. The results show that the seismic wave field is complicated by rugged surface,the wave type is converted to each other,the surface scattering is generated,the reflection wave is distorted,truncated or even submerged,and the noise-signal ratio is reduced. The proposed improved vacuum method can guarantee the stability and accuracy of algorithm,and the result is showed to be excellent.更多还原