The semi-airborne electromagnetic method (SAEM) has recently gained increased interest in geophysical exploration applications. For SAEM, ground-based transmitters are deployed within the area of interest or in its vicinity, and the induced magnetic is measured airborne. Because of the large footprint of extended transmitters, three-dimensional (3D) effects can have a significant impact on the gathered data and 3D modelling and inversion approaches must be employed for data analysis. Any 3D EM simulation is a resource-consuming task and efficient tools can therefore be useful to add data interpretation. In this study, 3D tomographic inversion of frequency-domain SAEM data was accomplished based on the integral equation (IE) method. The inversion was linearised by approximating the sensitivity matrix. We further employ the quasi-linear approximation to facilitate out quick forward modelling in the inversion which is tractable on field computers. While this approach sacrifices inversion accuracy for efficiency, we guide the inversion by introducing multinary constraints. These constraints impose a priori known conductivity values into the inversion process. Our results from synthetic and field data demonstrate the efficiency of our approach in achieving a coherent geophysical model that is consistent with geological data and findings from other geophysical techniques. This method provides a practical and capable solution for unveiling conductive 3D structures in the field.

半机载电磁法（SAEM）最近在地球物理勘探应用中引起了越来越多的兴趣。对于 SAEM，地面发射器部署在感兴趣的区域内或其附近，并在空中测量感应磁场。由于扩展发射机的占地面积较大，三维 (3D) 效应会对收集的数据产生重大影响，必须采用 3D 建模和反演方法进行数据分析。任何 3D EM 模拟都是一项消耗资源的任务，因此高效的工具可用于添加数据解释。本研究基于积分方程（IE）方法完成了频域SAEM数据的3D层析反演。通过近似灵敏度矩阵来线性化反演。我们进一步采用拟线性近似来促进反演中的快速正向建模，这在现场计算机上是易于处理的。虽然这种方法牺牲了反演精度以提高效率，但我们通过引入多元约束来指导反演。这些约束将先验已知的电导率值强加到反演过程中。我们的合成和现场数据结果证明了我们的方法在实现与地质数据和其他地球物理技术发现一致的连贯地球物理模型方面的效率。该方法为在现场揭示导电 3D 结构提供了实用且有效的解决方案。我们通过引入多元约束来指导反演。这些约束将先验已知的电导率值强加到反演过程中。我们的合成和现场数据结果证明了我们的方法在实现与地质数据和其他地球物理技术发现一致的连贯地球物理模型方面的效率。该方法为在现场揭示导电 3D 结构提供了实用且有效的解决方案。我们通过引入多元约束来指导反演。这些约束将先验已知的电导率值强加到反演过程中。我们的合成和现场数据结果证明了我们的方法在实现与地质数据和其他地球物理技术发现一致的连贯地球物理模型方面的效率。该方法为在现场揭示导电 3D 结构提供了实用且有效的解决方案。