Effect of Induced Polarization on Galvanic and Inductive Data: Where is it Stronger?

Abstract

Summary The phenomenon of Induced Polarization (IP) is commonly studied with galvanic methods, both in the field and in the laboratory. IP effects on inductive electromagnetic (EM) data have been reported since the early ‘80s, but the attention of the EM community in IP focuses mainly on exploration purposes, because strong chargeable anomalies trigger negative EM responses. In this study we show that the IP effect strongly affects EM data also in sand/clay environments, with a variety of acquisition systems, ranging from airborne EM, classic ground-based and portable systems for continuous ground acquisitions (the tTem system, towed by an ATV, and the Loupe system, mounted on backpacks). The effect on EM data simulated with these systems is much stronger than on data acquired with the galvanic method. This triggers bias in resistivity-only inversions, and makes data acquired with different systems incompatible with each other: data simulated with different systems cannot be fitted jointly. These findings highlight the importance of induced polarization on EM data, and open the way for new approaches for joint inversion of galvanic and inductive data, as well as for joint inversion of EM data acquired with different systems.