多分量波场的矢量法叠前深度偏移技术

Vector prestack depth migration of multi-component wavefield

本文研究了二维各向同性介质中两分量记录的矢量法叠前深度偏移方法———叠前逆时深度偏移方法。首先从弹性波波动方程出发,在交错网格空间中推导了各向同性介质中弹性波逆时延拓的高阶有限差分格式;然后从程函方程出发,采用逆时差分格式求解地下各点的地震波走时。为确保算法满足地震波传播的因果性条件及其对复杂模型的适应性,用扩展波阵面算法追踪波前并搜索全局极小,以上述方法的计算结果作为弹性波逆时偏移的成像条件,实现二维多分量资料的叠前逆时深度偏移。模型试算和实际单炮记录试验表明,叠前逆时深度偏移方法考虑了地震波的矢量特征,是一种有效的矢量波场处理技术。

The paper studied a vector prestack depth migration method—prestack inverse-time depth migration for two components records in 2D isotropic medium. Firstly, staring from the elastic wave equation, high-order finite-difference format of elastic wave inverse-time continuation in isotropic medium was deduced in staggering grid space; then, proceeding from the eikonal equation, the seismic travel time at each underground point was computed by inverse-time finite-difference format. In order to ensure the causality of seismic propagation and adaptability to complicated model, expanding wave front method was used to track wave front and search global minimum, taking above mentioned computational results as imaging condition of elastic wave inverse-time migration. The prestack inverse-time depth migration of 2D multi-component data can be realised. The tests of model and real single-shot records showed the prestack inverse-time depth migration considered the vector feature of seismic wave, which is an effective vector wavefield processing technique.