Volcanic activity of Campi Flegrei Caldera (Italy) during 2013-2020 from surface deformation mapping and modeling

The current unrest phase at Campi Flegrei Caldera, Italy from 2000 to present is evidenced by increasing seismicity rates and magnitude, gas emissions and remarkable ground deformation. We consider multi-technique geodetic data to constrain the recent surface deformations and study the possible hazard implications. Time-series from the COSMO-SkyMed satellite mission and GNSS data in the period 2013-2020 show an increasing rate of uplift at the caldera center, reaching a total of about 1 m in the town of Pozzuoli during 2010-2020. Horizontal deformation confirms the inflationary trend. Also, new GNSS seafloor measurements, located in the Gulf of Pozzuoli and available from 2017 to 2020, show a nearly radial pattern. The use of these data in the analysis, in addition to the inland GNSS and InSAR data, helps constraining the 3D pattern of deformation also in the submerged part of the Campi Flegrei caldera.

3D finite element models are developed including the elastic heterogeneous structure of the medium based on the newest seismic tomography of the area of Campi Flegrei. We consider the potential action of a plumbing system composed of a general (without fixing the shape a-priori) “central” source, and a deep tabular layer placed at 7.5 km depth.

The results show that the central source is placed below the caldera floor, at 4.5 km depth, and has a shape of a thick spheroid with axes ratio of about 0.8 and 0.5. The use of the sill-like source, as suggested by several previous studies for the 2011-2013 time window, lead to three-four fold higher misfits. We interpret our solution as a thickened sill for which the vertical dimension is not negligible such as for the sill-like source, but has a finite dimension of about half the horizontal extension.

No significant contributions from the deep tabular layer are evidenced by the inversions,  but the hypothesis of a deep reservoir cannot be fully ruled out, since its activity may be masked by the central shallower source. Also, the implementation of seafloor measurements leads to results compatible with the inland GNSS data alone. 

In order to understand the evolution of the current inflation process, the results are compared to previous models from the beginning of the present unrest phase (2011 - 2013) and also previous unrest phases (1980-1984).

This work is part of the multidisciplinary project LOVE-CF, financed by the Istituto Nazionale di Geofisica e Vulcanologia, to study the dynamics of Campi Flegrei caldera.