真地表动校叠加技术

随着地震勘探进入四川盆地周边大山区以及盆地内低、降速带极其严重的复杂近地表区，即便是采用最佳拟合的浮动基准面来处理，其剩余动校正量也足以破坏浅、中层数据叠加成像。研究动校时差理论发现，动校正量客观地存在于野外采集记录中，它不仅与炮检距有关，而且还与近地表、地下速度结构紧密相关，而与地表一致性静校正结果则无关。因此，动、静校正应该是相互独立而有序的两件事，不应该把两者混在一起，更不应该先作静校正、后作动校正。这是近些年来在研究浮动基准面所没有触及的实质性问题。为此，在分析大山区复杂近地表数据受剩余动校正量的实际影响之后，提出了把动、静校正分开，先作动校正、后作静校正处理，视浮动基准面为静校正中一个概念的一套真地表动校叠加技术。该技术方案既适应复杂近地表情况，又满足了各种复杂条件的要求，处理的地震资料浅、中层成像普遍得到改善，也更符合实际地质情况，为后续的深度偏移处理打下了基础。

True surface dynamic correction and stacking technique

With seismic exploration having been extended into the mountainous areas in the periphery of the Sichuan Basin and the complex near surface areas with weathered zones and/or subweathered zones in the interior of the basin, even if the floating datum with best fitting is used in processing the seismic data acquired in these areas, the residual normal moveout (RNMO) is still large enough to influence stacking and imaging of shallow to medium layers. Based on the theory of normal moveout correction, it is found out that dynamic correction does exist in field seismic records. Dynamic correction is related not only to the offset, but also to the near surface and subsurface velocity structures. However, it has nothing to do with the surface consistent statics. Therefore, dynamic correction and static correction should be two separate but sequential steps instead of one combined with each other. In addition, static correction can not be performed before dynamic correction. This is a new issue that has not been raised in floating datum research in recent years. Based on an analysis of the influences of dynamic correction on the processing of data acquired in mountainous areas with complex near surface conditions, a true surface dynamic correction and stacking technique is presented. Dynamic correction is performed separately with and also prior to static correction. This technique can not only adapt to the complex near surface conditions, but also meet the requirements of various complex conditions. The images of shallow and medium layers are generally improved and are more consistent with real geologic conditions, providing a solid foundation for subsequent depth migration in seismic data processing.