近地表层速度模型建立的波路径层析成像方法

Wavepath Traveltime Tomography for Near-Surface Velocity Model Building

在地震勘探中,近地表层剧烈变化的速度和厚度往往对偏移成像的质量产生重要影响。本文提出了1种回转波波路径层析成像和深度偏移相结合的浅层速度建模方法。该方法首先通过正演模拟和实际观测记录求得理论和实际初至波间的剩余时差,然后将其沿波动理论体系下的地震波波路径反投影,从而实现速度的迭代反演,最后利用基于反演速度结果的叠前深度偏移来确定近地表层的底界面。数值模型实验和实际资料处理都表明:该方法可为近地表层速度模型的建立提供1种有效的手段。

In seismic exploration,the highly varying near-surface velocity and depth can significantly influence the quality of migration imaging.This paper presents a new near-surface velocity model building approach which is based upon turning wavepath tomography and prestack depth migration.The velocity field is iteratively reconstructed by the back-projection of traveltime residuals between the computed and observed first arrivals along the turning wavepaths.This velocity field is then used for depth migration which offers the bottom interface of the near-surface velocity model.Numerical test and real data processing demonstrate that the method provides a useful way for near-surface velocity model building.