3D magnetic susceptibility imaging using EMI in-phase data: selected 3D inversion examples using small- and large-scale data sets

Rigid boom frequency-domain electromagnetic induction (FD-EMI) sensors based on a double magnetic dipole (loop–loop) geometry allows to rapidly characterize subsurface electrical and magnetic properties. Recent advances in instrumentation (including multi-configuration and multi-channel systems), high-resolution kinematic acquisition strategies, and fast 3D inversion algorithms allows the reconstruction of 3D subsurface models of electrical and magnetic properties with unprecedented detail.

In this study, we evaluate the potential of FD-EMI in-phase data for high-resolution 3D reconstruction of magnetic susceptibility (or permeability) using the recently developed 3D multi-channel deconvolution (MCD) approach. We tested the 3D MCD method on multiple data sets acquired in diverse igneous environments and with different FD-EMI systems in the context of archaeological prospection. Compared to conventional qualitative interpretation of FD-EMI in-phase data maps, the 3D MCD method significantly enhances the interpretability of the data by (1) enabling clear separation of subsurface features at different depth levels, (2) significantly improving lateral resolution and (3) revealing archaeological structures that remain invisible in the original measurements. These results highlight MCD as a key processing step that unlocks the full imaging potential of FD-EMI in-phase data.