Speaker
Description
The Einstein Telescope (ET), a next-generation underground gravitational-wave observatory planned in Sardinia (Italy), requires detailed subsurface characterization to ensure structural stability and minimal environmental noise. Understanding the distribution of fractured zones and groundwater systems within the crystalline basement is critical, as these factors directly affect excavation conditions, hydrogeological behavior, and seismic noise sources. We present preliminary results of a large-scale Airborne Electromagnetic (AEM) survey aimed at reconstructing a high-resolution 3D resistivity model of the subsurface down to ~500 m depth. The SkyTEM system was selected for its ability to combine near-surface resolution with a high transmitter moment, ensuring adequate depth of investigation in a highly resistive geological environment. The survey covers ~450 km² (~3000 line km) with an average flight-line spacing of 170 m. AEM data are inverted using both deterministic and probabilistic strategies. Deterministic inversion provides a best-fit resistivity model constrained by geological data, while probabilistic approaches quantify the likelihood of encountering fractured or water-saturated zones — a key input for risk mitigation and design optimization. Conductive anomalies are interpreted as fractured or fluid-bearing zones; resistive domains correspond to intact crystalline rock. Simultaneously acquired airborne magnetic data contribute to the identification of structural lineaments and lithological contrasts, complementing the AEM interpretation. Expected outcomes include: (i) high-resolution 3D resistivity models, (ii) probabilistic maps of fracture distribution, and (iii) identification of zones of hydrogeological and geotechnical significance. These results will support decisions on tunnel alignment, excavation strategy, and groundwater management for the ET underground infrastructure.