摘要
Engineering seismic exploration aims at shallow imaging which is confused by statics if the surface is uneven. Direct pre-stack depth migration （DPDM） is based on accurate elevations of sources and receivers, by which static correction is completely abandoned before migration and surely the imaging quality is remarkably improved. To obtain some artificial shot gathers, high-order staggered-grid finite-difference （FD） method is adapted to model acoustic wave propagation. Since the shot gathers are always disturbed by regular interferences, the statics still must be applied to supporting the interference elimination by apparent velocity filtering method. Then all the shot gathers should be removed back to their original positions by reverse statics. Finally, they are migrated by pre-stack reverse-time depth migration and imaged. The numerical experiments show that the DPDM can ideally avoid the mistakes caused by statics and increase imaging precision.
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。
