DInSAR data from the last three decades reveals persistent large-scale features and local anomalies in the ground deformation of Campi Flegrei, Italy.

Following a quiescent period of 3,000 years and several centuries of subsidence, with only one eruption in 1538, Campi Flegrei has experienced intermittent unrest since 1950. The 1982-84 uplift episode was followed by a period of subsidence, but since the early 2000s there has been almost continuous uplift, accompanied by geochemical anomalies and seismicity. In 2012, the Major Risk Commission raised the Alert Level from green to yellow.
SAR images from different missions have made it possible to monitor the deformation field of Campi Flegrei since the 1990s. In particular, the periods 1993–2010 and 2015–present have been covered by the ERS/ENVISAT and Sentinel-1 missions of ESA, respectively. The time gap between these two periods has recently been filled using Radarsat-2 images (Amoruso et al. 2025). Consequently, we were able to conduct a systematic analysis of Campi Flegrei deformation over the last three decades. We have employed linear regression models and blind source separation techniques (Principal Component Analysis and Independent Component Analysis).
The preliminary results suggest the coexistence of two stationary deformation fields throughout the entire investigated period. The field with the larger amplitude has dimensions similar to those of the caldera, and its temporal history is almost the same as that of the area of maximum uplift. This field is consistent with a pressurised sill located around 4 km deep. The other field is less conspicuous, but it may have even more significant implications. It is more extensive, it is shifted eastwards relative to the centre of the caldera, it is characterised by uplift since at least the beginning of the available DInSAR time series, and it is consistent with a deep pressurised deformation source. In addition, anomalies in the Solfatara area (Amoruso et al. 2014) and in the Accademia Aeronautica area (Giudicepietro et al. 2024) are confirmed and detailed. In this way, the deformation of Campi Flegrei is fully satisfied within data uncertainties throughout the entire period under investigation.

References 

Amoruso, A. et al., J. Geophys. Res. Solid Earth, 119, 858–879, 2014.
Amoruso, A. et al., Remote Sens., 17, 3268, 2025. 
Giudicepietro, F., et al., Int. J. Appl. Earth Obs. Geoinf., 132, 104060, 2024.