GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 3.2 GNGTS 2024 Below, in fgure 3 , follows an example of representaton of the results in a 2D map, representng in color the distorton, as computed following equaton 2, as a functon of chargeability and resistvity of the frst layer. Figure 3. Representaton of the IP Distorton (eq.2) for the Loupe Z component, for two layers models. The frst layer thickness, Tau and C parameters are kept fxed in the ttle, while the Resistvity and Chargeability vary along the axes. The colorscale represents the diference, in percentage, between the IP afected halfspace and the purely resistve halfspace forward responses. IP afects signifcantly the forward response even with low values for chargeability and high values for the tme constant. The increase of the distorton follows the increase in chargeability, and already from 10 mV/V an error higher of 5% is reached. This spread of IP efects is linked to the two-layers confguraton with resistve bedrock: the IP EM vortex currents, which fow in opposite directon of the eddy currents, propagate slowly in the second layer and dominate the current fow. In this confguraton it is also interestng to see how even for a tme constant of 0.3 ms it is possible to detect the IP efects above the noise level, also with a 75 Hz instrument. Figure SEQ Figure \* ARABIC 2. Comparison of the forward responses for the two layers model,