First superconducting gravity station at Campi Flegrei caldera: Installation, data processing and noise assessment for future volcano monitoring

We report on the realization of the first superconducting gravity (SG) station at Campi Flegrei caldera (Southern Italy). The processing of 1 year of gravity recording is described in detail, with emphasis on the reduction of non-volcanic effects, aiming to ascertain its reliability for future volcanological studies. A precise local tidal gravity model is obtained. Atmospheric corrections were tested both in time and frequency domains showing that an “hybrid” method (local admittance function + global atmospheric models) and Fourier band-pass filtering are the most effective ones. Spectral analysis revealed higher noise levels than previous installations in non-volcanic areas, likely due to a combination of micro-seismicity and anthropogenic sources. We found consistent peaks in the noise spectrum at periods corresponding to the seiches of the Pozzuoli Bay, indicating relevant non-tidal ocean loading contributions. The SG drift is examined in detail, taking advantage of time-lapse relative gravity measurements (RG). A good agreement of the long-term SG residuals with RG ones turns out, evidencing a decrease of about 40 μGal in the time span 10/2024–10/2025, which is correlated with the observed ground uplift. Simple simulations are performed to infer the sensitivity of the SG station to mass variations of volcanic origin. It turns out that the SG's great sensitivity to mass changes is being hindered by the current level of precision in geodetic observations, which are routinely used to remove the contribution of vertical ground deformation.