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目前用于自激自收(水平迭加)剖面偏移的上行波波动方程,由于忽略了u_(zz)项,只适用于倾角小于15°地层的偏移,通常称为15°偏移方程。最近[1]中介绍了一种改进了的上行波波动方程,由于它仅忽略了u_(zzz)项,因此适用于更大倾角(小于45°)地层的偏移,称为45°偏转方程。其在波数域实现偏移时,对大倾角取得了更好的效果,并进一步提出波数—频率域的偏移方法。本文根据[1]中提出的45°偏移方程,给出在普通的距离—时间域实现偏移的差分方法。它与15°偏移方程相比,方法类同,只要将15°偏移程序稍加修改即可实现,增加计算工作量约四分之一。最后给出当延拓层时间间隔大于记录时间采样间隔时,在延拓层时间间隔内偏移值的内插公式。
The up-going wave equation currently used for the self-excitation self-excitation (horizontal superposition) profile migration, which omits the uzz term, applies only to the offset of the dip less than 15 °, commonly referred to as the 15 ° offset equation . An improved wave equation for upgoing waves was introduced recently [1]. Since it only omits the uzzz term, it is suitable for strata with larger inclination (less than 45 °) and is called the 45 ° deflection equation . When it achieves the offset in the wave number domain, it achieves better effect on large dip angle and further proposes the method of wave number-frequency domain offset. Based on the 45 ° offset equation proposed in [1], this paper gives the difference method of offset in normal distance-time domain. Compared with the 15 ° offset equation, the method is the same, as long as the 15 ° offset program can be slightly modified to increase the computational workload by about a quarter. Finally, the interpolation formula of the offset value in the extension interval is given when the extension interval interval is greater than the recording interval sampling interval.