Unravelling the electrical structure in a sector of the Irpinia fault with a 3D magnetotelluric investigation.

In conjunction with the the DEnse mulTi-paramEtriC observations and 4D high resoluTion imaging (DETECT) experiment, n. 30 broad-band magnetotelluric (MT) soundings were carried out between 2007 and 2022 obtaining impedance tensor estimates in the period range for $10^{-1}$ to $3\times 10^{+3}$ s. These soundings covering a wide sector ({80 $\times 60$ km) of the Irpinia fault system, which generated the largest Italian event in the last 100 years with ${Ms}=6.9$ (1980). Mefite d'Ansanto, the largest source of natural $CO_2$ gas emission measured on the Earth in a non-volcanic environment, also falls in the investigated area. In this communication we show the three-dimensional (3D) resistivity model of the survey area aimed to infer valuable information on the deep structures and processes taking place into the subsoil. This will be possible thanks to the combined high investigation depth of the MT method and its sensitivity to lateral and vertical electrical conductivity variations related to fluids presence and/or temperature changes. The model interpretation will also benefit from the integration with other geophysical (mainly seismic) observations.