真振幅全倾角单程波方程偏移方法

True amplitude turning-wave one-way wave equation migration

（1.CGGVeritas公司, 美国得克萨斯休斯敦 TX 77072；2.中国科学院数学与系统科学研究院，北京 100080；3.佛罗里达矿业大学，美国佛罗里达丹佛 CO 80401）

CGGVeritas, Houston, TX 77072, USA

常规单程波方程偏移方法不能保持声波波场的传播振幅，大倾角的波场振幅被削弱，同时，波场的传播受到90°倾角的限制。针对这些问题，提出了真振幅全倾角单程波方程偏移方法。该方法首先向下延拓激发波场和接收波场，然后再将回转波场向上传播，从而将波场的传播角度范围拓宽到0°～180°，可以对任意倾角的构造进行成像，并通过引入真振幅校正项加强了大倾角结构的成像。将常规单程波方程偏移方法和真振幅全倾角单程波方程偏移方法应用于墨西哥湾地区复杂盐丘模型和实际资料，结果显示，盐丘的陡倾角侧翼边界在常规单程波偏移中不能得到很好成像，经过全倾角单程波方程偏移处理后被清晰地显示出来。真振幅全倾角单程波方程偏移方法的计算量大约是常规方法的两倍。

The conventional one-way wave equation migration cannot preserve the propagation amplitude and only computes those wave fields whose propagation angles are smaller than 90°. Therefore, steeply dipping reflectors are often absent from its images. We propose a modified version of one-way wave equation migration, called true amplitude turning-wave one-way wave equation migration, which incorporates true amplitude corrections to enhance steep dips and propagates wave fields to any possible directions. With this new method, the turning waves can be properly imaged and the imaging capability of one-way wave equation greatly improved. We have applied the method in complex synthetic and real data in the area of Mexico Gulf. The migrated results show much better defined salt boundaries and the steeply dipping salt flanks and the overturning salt bottom are well imaged. The computational cost of the proposed method is about twice as much as that of the conventional one-way wave equation migration.