Comparison of tTEM-IP and ERT-IP : cases from mine tailing sites in Sweden

• The induced polarization (IP) effect can be studied using both galvanic and inductive methods. Here we study IP and its manifestation in transient electromagnetic (TEM) data from a tTEM system and in time-domain electric resistivity tomography (ERT) data. Since the two methods are sensitive to two different frequency ranges, a direct IP spectrum comparison is not possible. Instead, we assess the IP resolution and compare both resistivity and chargeability inversion results. We show that tTEM data recorded in highly resistive environments with high IP, suffer from fast-decaying transients and sign-changes, which makes it difficult to resolve the true resistivity and IP model due equivalences. A comparison of the maximum phase shifts from two mine tailing sites shows that the chargeability structures gained from the inversion of tTEM data to some degree follow the structures of the chargeability resolved from the ERT data. However, the magnitudes of the resolved phases are generally below 50 mRad for ERT, but up to 500 mRad for tTEM. This indicates that different polarization mechanisms are dominating within the different frequency ranges of the tTEM and ERT methods.

Subject headings

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Geofysik (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Geophysics (hsv//eng)

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