ABSTRACT We propose the approach to 3D inversion of airborne electromagnetic data, which is intended for discovering subvertical bodies overlapped by essentially inhomogeneous conductive layers. The approach is based on the geometric inversion in which a geoelectrical medium is parameterized with the use of block structures. During the inversion, the coordinates of the borders between the blocks and the rows of the blocks as well as resistivities inside them are determined. In order to solve the forward problem of the airborne electromagnetic survey, we use the non‐conforming optimized mesh with the hexahedral cells, which enables us to reduce the number of degrees of freedom and smoothly approximate the curved borders of a geological medium. For a more reliable discovery of subvertical objects, we propose to carry out 3D inversions at several rotations of block structures relative to the flight lines. The workability of this approach is demonstrated using the data which are synthesized for complex geoelectrical models with topography, inhomogeneous overlapping layers and target subvertical bodies oriented differently relative to the flight lines. The results of this investigation show that, in some way or other, the elongated subvertical object is discovered and its orientation (the direction of its long side) is defined at different rotations of block structures used in 3D inversions. However, the most accurate recovery of the subvertical object length is achieved when the direction of its long side almost coincides with the direction of one of the block structures axes. Thus, the block structures rotations allow not only more reliably discovering a target object in complex geoelectrical conditions, but also more exactly defining its orientation and length.

中文翻译：

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机载数据的 3-D 反演，用于检测由具有地形的不均匀导电层重叠的细长的亚垂直体

摘要我们提出了机载电磁数据的 3D 反演方法，该方法旨在发现由本质上不均匀的导电层重叠的亚垂直物体。该方法基于几何反演，其中使用块结构参数化地电介质。在反演过程中，块之间的边界和块的行以及它们内部的电阻率的坐标被确定。为了解决机载电磁测量的前沿问题，我们使用六面体单元的非一致性优化网格，这使我们能够减少自由度数并平滑地逼近地质介质的弯曲边界。为了更可靠地发现亚垂直物体，我们建议在块结构相对于飞行线的几次旋转中进行 3D 反演。使用为复杂地电模型合成的数据证明了这种方法的可行性，这些模型具有地形、不均匀的重叠层和相对于飞行线定向不同的目标亚垂直体。这项调查的结果表明，以某种方式发现了细长的近垂直物体，并且在 3D 反演中使用的块结构的不同旋转时定义了它的方向（其长边的方向）。然而，当其长边的方向几乎与块结构轴之一的方向重合时，实现了近垂直物体长度的最准确恢复。因此，