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对通过有横向速度梯度的地层的信号,计算地震反射时间的普通方法,是在震源和接收器的中点上内插均方根速度并对直射线反射时间方程使用这个速度。当考虑将该方法用于共深度点迭加时,它可严重地降低偏移迭加的质量,在那里比较大的炮检距能导致反射时的较大误差。为了计算线性横向速度梯度存在时候的最小反射时,我们描述了一种两级,迭代的最佳化方法,它是建立在梯度投影算法基础上的。用理论合成的例子说明了这个结果。
A common method of calculating seismic reflection times for signals passing through formations with lateral velocity gradients is to interpolate the rms velocity at the midpoint of the source and receiver and use this velocity for the ray reflection time equation. When considering this method for co-depth point superposition, it can severely reduce the quality of the offset superposition, where a larger offset can lead to larger errors in reflection. In order to calculate the minimum reflection at the time when a linear lateral velocity gradient exists, we describe a two-stage, iterative optimization method that is based on a gradient projection algorithm. An example of theoretical synthesis illustrates this result.