论文详情
复杂山地近地表速度结构复杂,横向速度变化快,建模精度低,严重影响后续偏移成像质量。初至波层析反演是解决复杂近地表速度建模的有效手段,但面临着计算精度和计算效率均需提高的问题。为此,提出了一种基于改进快速扫描法的多尺度近地表层析速度建模方法,分别从正演和反演两个方面提升初至波层析反演精度。在正演方面,提出基于改进快速扫描法的初至波走时计算方法,应用双线性插值技术,在保持快速扫描算法高效率的基础上提高计算精度;在反演方面,利用改进散射积分法求解层析矩阵,并通过多尺度层析策略提高反演精度。将提出的近地表建模方法应用于丁山工区的实际资料处理,结果表明,改进快速扫描法使得正演计算量大幅度减小,在其它条件不变的情况下,多尺度层析策略反演得到的速度模型精度高,偏移成像剖面与原始剖面相比,近地表范围内同相轴连续性更好,为后续中深层速度建模提供了良好的保障。
关键词：
The near-surface velocity of mountain areas is complex and exhibits large lateral variations,resulting in difficult high-precision velocity modeling and significantly affecting the quality of migration.First-arrival tomography is an effective method to build complex near-surface velocity structures,but computational accuracy and efficiency still need to be improved.A multi-scale near-surface tomographic velocity modeling method,based on an improved fast sweeping method,is proposed to improve the accuracy of first-arrival tomography from forward and backward inversions.In forward modeling,we propose the first-break traveltime calculation method,based on the improved fast sweeping method (FSM).First,the bilinear interpolation technique is introduced to improve calculation accuracy while maintaining the efficiency of FSM.In velocity building,the improved scattering integral method is used to solve the tomographic matrix,and the inversion accuracy is improved by a multi-scale tomography strategy.The proposed near-surface modeling method was applied in actual data processing in the Dingshan area.Results show that the improved FSM significantly reduced the forward computation.The migration profile,based on the velocity and obtained by the multi-scale tomography strategy,was more continuous in the near-surface area than that of the original profile,providing better data support for subsequent medium and deep velocity modeling.
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国家科技重大专项(2017ZX05036005-006)资助。