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15°有限差分串联偏移在实际应用中存在过偏移问题。笔者通过理论推导和试验,证明过偏移产生于差分误差的积累,而差分误差的大小又取决于速度、频率、界面倾角、空间采样间隔、时间采样间隔、深度步长和差分方式等因素的影响。在此基础上,文中提出了一种可行的差分误差补偿方法,即在原差分波动方程中引入补偿系数R,就可以克服过偏移问题。补偿系数R是△t(时间采样间隔)、△x(空间采样间隔)、△τ(深度步长)、V(层速度)、f(频率)、φ(界面倾角)和B(二阶差分近似系数)的函数。文中分别讨论了这些参数对R的影响,并给出确定R的办法。由实际资料试验说明,该方法保持了原有15°近似方程的优点,并能使60°倾角的界面达到正确的归位。
15 ° finite difference tandem offset exists in practical application over-migration problem. The author derives and tests the theory that the over-migration is caused by the accumulation of differential error, which in turn depends on such factors as velocity, frequency, inter-face tilt, spatial sampling interval, temporal sampling interval, depth step and difference mode influences. On this basis, a feasible compensation method of differential error is proposed in this paper. That is, the introduction of compensation coefficient R into the original differential wave equation can overcome the over-migration problem. The compensation coefficient R is a function of Δt (time sampling interval), Δx (spatial sampling interval), Δτ (depth step), V (velocity of layer), f (frequency), φ Approximate coefficient) function. The paper separately discusses the influence of these parameters on R and gives the method to determine R. The experimental results show that this method retains the advantages of the original 15 ° approximation equation and enables the correct homing of the 60 ° dipole interface.