ERS/ENVISAT, Radarsat2 and Sentinel1 SAR images: ground deformation at Campi Flegrei and Vesuvio, Italy, since 1993

The densely populated area of Naples, Italy, situated between the Campi Flegrei caldera and the Vesuvio volcano, is recognised as one of the most hazardous regions on the planet. Over the past 15,000 years, numerous eruptions have occurred at Campi Flegrei, accompanied by the resurgence of the centre of the caldera. Following a period of quiescence spanning 3,000 years and several centuries of subsidence, Campi Flegrei experienced another eruption in 1538, preceded by an increase in seismic activity and uplift. Since the 1950s, Campi Flegrei has experienced intermittent unrest, with four main episodes occurring between 1950–1952, 1969–1972, 1982–1984, and 2005 to the present. The unrest between 1982 and 1984 was followed by prolonged subsidence, and there has been an almost continuous uplift since the early 2000s. Somma-Vesuvio is a stratovolcano with a summit caldera (Mount Somma) and a recent cone (Mount Vesuvio) resulting from several Plinian eruptions. The most recent Plinian eruption of Vesuvio occurred in 79 AD, with sub-Plinian eruptions following in 472 and 1631, subsequently succeeded by semi-persistent activity that endured until 1944.The eruptive histories of Campi Flegrei and Vesuvio are different, and past erupted products show dissimilar characteristics. However, the compatibility of past erupted products with the possible existence of a single magma accumulation layer at a depth of 8–10 km is noteworthy, with geophysical investigations also suggesting the presence of this layer.
Recent studies have utilised ERS/ENVISAT (1993–2010) and Sentinel1 (2015–present) SAR data to demonstrate that ground deformation is partially attributable to sources at a depth of approximately 8 km during the Campi Flegrei uplift. Furthermore, the findings indicate that a depressurisation occurred at depth beneath Vesuvio in the early 2000s, and that there were possible deep interactions between the two volcanoes during the transition period between subsidence and uplift at Campi Flegrei.
From 2010 to 2015, the available COSMO-SkyMed images acquired in ascending orbit did not cover the western end of the Campi Flegrei, and the descending orbit images did not cover the area around Vesuvio. However, the ESA's PP0094512 project, entitled "Campi Flegrei caldera evolution in between ERS/ENVISAT and Sentinel1 missions", has enabled the generation of deformation time series from Radarsat2 images encompassing the entire volcanic area. This achievement was made possible by the development of a hybrid procedure; this procedure consists of using various free or open-source software in sequence — SNAP (https://step.esa.int/main/download/snap-download/), GMT (https://www.generic-mapping-tools.org/), gdal (https://gdal.org/), GMTSAR (https://topex.ucsd.edu/gmtsar/) — with appropriate adaptations. The validity of the series is confirmed through comparison with GNSS (Global Navigation Satellite System) data from the INGV NeVoCGPS network.
The first results obtained by combining the ERS/ENVISAT, Radarsat2 and Sentinel1 data, and in particular the evolution of non-moving statistically independent deformation sources, are presented.