原作者：M. Elwaseif
翻译自期刊：Computers & Geosciences
Multi-frequency electromagnetic (EM) induction tools are increasingly used for hydrogeophysics applications.
多频电磁法近来被广泛用于水文地质等领域。
In contrast to the galvanic resistivity imaging method, EM tools are less labor intensive to operate, offer large-scale coverage, and can be used over almost any terrain (except for urban areas).
与电阻率成像方法相比，多频电磁的施工操作更便捷，具有大范围的覆盖范围，几乎可以用于任何地形(城市地区除外)。
These advantages have led to [1] the development of small-loop multi-frequency EM systems that can record high density data (usually 3–5 soundings per linear meter) that are tagged with location information (x, y and z), typically using a global-positioning system (GPS), that can provide very high resolution (centimeter-level); and [2] increased interest in airborne EM surveys that can cover large areas (10's to 1000s of km 2 ) and image to ~100 m depth.
这些优势激发了[1]小环路，高采样(1米3-5个测深点)的多频电磁系统的诞生，[2]可覆盖很大面积（数十到数千平方公里）的航空电磁调查，探测深度100米以内。
However, inverting multi-frequency domain EM data to obtain meaningful models is challenging
because [1] it is time consuming especially when dealing with three-dimensional (3D) problems, [2] data commonly are contaminated with both systematic instrument errors and random noise , and [3] the depth of investigation (DOI) varies with conductivity structure and meas