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工程地震主要解决浅中层地质问题,然而在复杂地表条件下静校正会严重影响浅中部地层的成像精度。基于起伏地形条件下的直接叠前偏移,通过研究适用于精确炮检点高程的新的成像条件,完全避开了静校正处理,从而提高成像质量。首先从正演出发,利用高阶交错网格有限差分法精确模拟地表起伏条件下的纵波波场,并得到复杂地表条件下的单炮记录。再将炮检点通过静校正方法进行野外一次静校正,以便于利用视速度滤波法除去规则干扰。然后,再进行反静校正处理,把各道数据又重新恢复到野外实际高程点,最后直接利用带地形的单炮记录进行叠前深度偏移。模型结果表明,直接叠前偏移处理能够很好地避免静校正带来的误差,大幅度地提高浅中部地层的成像精度。
Engineering earthquakes mainly solve shallow and middle geological problems. However, under complex surface conditions, static correction will seriously affect the imaging accuracy of the middle and lower strata. Based on the direct prestack migration under undulating terrain conditions, the static image correction is completely avoided by studying the new imaging conditions suitable for the accurate elevation of the shotpoint, so as to improve the imaging quality. First of all, from the forward modeling, the high-order staggered grid finite difference method is used to accurately simulate the longitudinal wavefield under the surface undulation, and the single shot record under complex surface conditions is obtained. Then the shotguns through the static correction method for a static correction in order to facilitate the use of apparent velocity filtering to remove the rules of interference. Then, anti-static correction is carried out to restore all the data to the actual elevation point in the field. Finally, the prestack depth migration is directly performed by using the single shot record with the terrain. The model results show that the direct prestack migration processing can well avoid the error caused by static correction and greatly improve the imaging accuracy of the middle and lower strata.