数据类型对三维广域电磁法勘探效果的影响

The Impact of Data Types on the Effectiveness of 3D WFEM

摘要: 为探讨不同数据类型对三维广域电磁法反演成像效果的影响，文章基于三维数值模拟与反演计算，对电场与磁场不同分量的数据响应特征及其成像能力进行了系统分析。采用谱元法实现三维正演计算，并结合有限内存拟牛顿算法(L-BFGS)构建三维反演框架。通过设计典型低阻异常模型，对Ex复分量、振幅数据以及Hy、Hz复分量及其组合形式进行了对比反演研究。结果表明：Ex复分量反演在异常体形态恢复、边界刻画及电阻率定量估计方面明显优于单纯振幅反演；Hy分量对横向电性变化敏感性较弱，单分量反演成像能力有限；Hz分量对三维结构具有一定响应优势，但分辨率仍低于电场分量。多分量联合反演虽可增强数据约束，但同时可能加剧模型多解性，对正则化参数与结构约束依赖更高。研究结果为广域电磁法三维反演数据类型的合理选择提供了理论依据。

Abstract: To investigate the impact of different data types on the imaging effects of 3D WFEM, this paper conducts a systematic analysis of the response characteristics and imaging capabilities of different components of electric and magnetic field data based on 3D numerical simulation and inversion calculations. The spectral element method is used to achieve 3D forward modeling, and combined with the L-BFGS algorithm, a 3D inversion framework is constructed. By designing typical low-resistivity anomaly models, comparative inversion studies are conducted for the Ex complex component, amplitude data, as well as Hy and Hz complex components and their combinations. The results show that: inversion using the Ex complex component is significantly better than simple amplitude inversion in terms of recovering the anomaly shape, delineating boundaries, and quantitatively estimating resistivity; the Hy component has weak sensitivity to lateral electrical variations, and single-component inversion has limited imaging capability; the Hz component has certain advantages in responding to 3D structures, but its resolution is still lower than that of electric field components. Although multi-component joint inversion can enhance data constraints, it may also exacerbate model non-uniqueness, increasing dependence on regularization parameters and structural constraints. The results provide a theoretical basis for the rational selection of data types in 3D regional electromagnetic inversion.