高斯束线性正演模拟方法研究

Gaussian-beam linear forward modeling

Born近似描述了介质扰动引起的一次散射现象,是线性化地震反演的重要基础。笔者基于Born近似,利用高斯束传播算子表征格林函数,推导得到基于地下慢度扰动的一次反射波场理论公式,称这种反射波场的模拟为高斯束线性正演。在编程实现方法的基础上,通过对绕射体模型、复杂砂砾岩体模型以及起伏地表模型进行数值模拟,并对模拟产生的多炮记录进行偏移试验,结果表明:(1)高斯束线性正演能够准确地模拟出不含直达波和多次波的一次反射波信息;(2)对高斯束线性正演产生的多炮记录进行偏移能够恢复模型构造特征;(3)高斯束线性正演易于实现面向目标的数值模拟。

Born approximation describes the primary scattering response of perturbed medium, which is the basis of linearized seismic inversion.Based on Born approximation ,we derive the primary reflected wavefiled propagation formula by expressing the Green＇s function as a Ganssian-beam summation.The simulation of primary reflected waves is called Gaussian-beam linear forward modeling.On this ba- sis,we perform numerical test by using the diffractors model,the glutenite model and the irregular surface model, and compare our re- suits with those generated by wave equation modeling.Besides, we implement migration with corresponding synthetic seismograms generated by Gaussian-beam linear forward modeling.Numerical results indicate：First, Gaussian-beam linear forward modeling can accurately produce recorded data with multiple and the direct wave muted;Second, migration with synthetic seismograms generated by Gaussian- beam linear forward modeling can image corresponding subsurface structures ; Third, target-oriented modeling can be carried out naturally.