We present a robust method to estimate the incident angle field based on the one-way propagator. The employment of monochromatic wave field is to reduce the extrapolation time dramatically and ensure the generation of the incident angle field in the whole imaging space. This incident angle field estimation method has high computational efficiency and can be applied in getting angle gather in one-way wave equation depth migration scheme. Comparison with depth migration, the cost of incident angle field estimation can be omitted. The proposed algorithm is free of smoothness of velocity model and hence can avoid large incident angle variation with small velocity perturbation compared to the traditional ray tracing or travel-time gradient picking method. This means the proposed angle field estimation method is more suitable for real velocity model and match well with the one-way wave equation prestack depth migration scheme. Computation of incident angle fields of the 2-D, 3-D layered and complicated structured models show the high computational efficiency, stability and precision of the proposed algorithm.%基于单程波深度延拓方法,发展了一种地震波入射角度计算方法.入射角度的计算仅利用简谐波场,可得到整个成像区域内所有点的入射波波前面方向.该方法具有较高的计算效率,可服务于合成角道集等深度偏移方法；与偏移算法相比,其计算量几乎可以忽略.与射线法或基于走时梯度的入射角度计算方法相比,本文方法更稳健,避免了速度场的微小变化导致的入射角较大变化,因此更适用于实际偏移速度模型,也与波动方程深度偏移方法更匹配.数值算例表明,本文方法既有较高的计算效率又有很好的精度,且有很好的稳定性.
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