b'David Annetts best of Exploration GeophysicsFeatureFigure 2.Conductivity-depth image (CDI) of slightly noisy 1992 QUESTEM data leads to false indications of both poor and good conductors at depth. The profile is 20 km long and the geology consists of sediments covering a Proterozoic basement.Figure 3.CDI section of the same line as Figure 2 derived from all-time data. There are no obvious artefacts or instabilities at depth.47 PREVIEW OCTOBER 2020'