Induced polarization effects in EM data: The Loupe system case study.

It is nowadays accepted, both in industry and in academy, that Induced Polarization (IP) affects electromagnetic (EM) data, when these are collected over a medium characterized by strong IP properties. With this study we want to verify if and how IP effects are detectable also by the new ground-EM system Loupe. The Loupe system is a two-operator walkable transient EM (TEM) profiling system designed to image the electrical properties of the ground with a high lateral and vertical resolution. In order to map the IP effects, we set up a large data space and model space analysis. IP is modelled with frequency-dependent resistivity in a series of two-layer synthetic models, and thousands of forward responses varying the model's parameters are calculated. We thus compare the forward responses affected by IP with the equivalent purely-resistive ones. We find that significant IP effects are present on most models, also with moderate and low polarization properties. These effects, if not modelled, bring to incorrect estimation of conductivity-thickness parameters when a resistivity-only inversions are carried out.