The Italian Fiducial Gravimetric Network based on high-precision continuous gravity measurements

INGV is currently developing the Italian Fiducial Gravimetric Network, which will consist of approximately ten stations evenly distributed across the national territory. The network will include several INGV stations, equipped with superconducting or absolute (quantum and ballistic) gravimeters, currently the only instruments capable of providing high-precision and stable gravity measurements over long periods, operating in continuous or quasi-continuous mode.

The primary aim of the network is to monitor long-term and long-wavelength variations of the gravitational field over the Italian territory. This network supports the newly established National Reference Gravimetric (G0) and Height (H0) Network. Four stations of the network managed by INGV — Cascina, Napoli, Nicolosi and Sos Enattos — are already operational and acquiring data. Among these four stations, two are equipped with superconducting relative gravimeters (iGravs, manufactured by GWR Instruments): iGrav#25 at Nicolosi and iGrav#70 at Sos Enattos. The Nicolosi station, operational since 2016, is of particular interest for the monitoring of Mt. Etna volcano. The Sos Enattos station, located at the Italian candidate site for the Einstein Telescope (the future European gravitational-wave observatory), was installed in September 2025 at a preliminary location and will be relocated to its final site in early 2026. In November and December 2025, two Absolute Quantum Gravimeters (AQGs, manufactured by Exail) were deployed at Cascina (AQG-A09, installed at the EGO site, where the Virgo gravitational-wave detector is hosted) and Naples (AQG-B06, installed at the CeSMA, University of Naples “Federico II”). All stations are remotely controlled.

Since the installation of each gravimeter, daily analysis of the incoming signal has been carried out. Here we present preliminary results from the already available data. In this first stage, the main objective has been to characterise the recorded signals, evaluating instrumental sensitivity and stability, as well as analysing the environmental noise. In the subsequent phase, the focus will move to the estimation and separation of local contributions from regional-scale signals. To this end, the sites have been or will be equipped with sensors to measure key meteorological parameters, GNSS receivers to monitor ground deformation and, where possible, piezometers to measure the oscillations of the local groundwater table.