GNGTS 2021 - Atti del 39° Convegno Nazionale

453 GNGTS 2021 S essione 3.2 High-Resolution Electrical Resistivity Measurements A 2D high-resolution ERT survey was performed in an area of ​(640 x 429) m 2 to west of the Ailano town (CE) (~260 m above sea level). The survey consisted of three 2D resistivity tomographies indicated in Fig. 2a with ERT1, ERT2 and ERT3. The area has a slightly uneven morphology, with a difference in altitude of 12 m between the ERT1 and the ERT2, while the ERT3 has an altitude variation of 26 m, passing from 159 m a.s.l. to 133 m a.s.l. The data acquisition was carried out by using the Syscal Pro 96 Switch georesistivity meter (IRIS Instruments) in multi-electrode configuration with an electrode spacing of 9 m. The choice of the pole-dipole electrode configuration allowed an investigation depth of about 90 m for the ERT1 and ERT2 profiles, 423 m long, and of 140 m for the ERT3 profile, 639 m long and orthogonal to the first two profiles. Results The collected apparent resistivity data were inverted by the RES2DINV software (Loke and Barker, 1996) by taking into account the rough surface topography of the profiles. For all the three ERTs, five iterations were performed providing RMS errors ranging from 5.3% to 10.6%. Fig. 2b displays the obtained inversion results. As it can be seen, starting from the ground level, the investigated sections are characterized by large areas with relatively low resistivity values, ranging from 15 Ωm to 40 Ωm (green zones in Fig. 2b), which, in some sectors, are observed up to the maximum exploration depth. Based on the lithology of the survey area, these resistivity values can be associated with the presence of alluvial (silts and clays) and pyroclastic deposits. The presence of more resistive nuclei (150 ≤ ρ ≤ 250 Ωm) within these relatively conductive zones, which are observed in both ERT1 and ERT2 profiles Fig. 1 - Simplified geological map of the southern Apennines showing the non-volcanic gas emission sites and the location of the Ailano (CE) study area (red rectangle).