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Geodetic Modelling of Ground Deformation at Campi Flegrei Caldera (Italy) During the 1985--2003 Subsidence Phase

Ana Astort 1, Elisa Trasatti1, Carlo Del Gaudio1, Prospero De Martino1, Valerio Acocella2, Mauro Aantonio Di Vito1

  • Affiliations: 1 Istituto Nazionale di Geofisica e Vulcanologia, Italy  2 Department of Science, Università degli Studi di Roma Tre, Rome, Italy 

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 205

  • Programme No: 3.10.9

  • Theme 3 > Session 10

Abstract

Campi Flegrei caldera, a 15 km-wide volcanic system located west of Naples, hosts nearly 400'000 people. Its last eruption took place in 1538 CE. The caldera experienced periods of unrest in the 1950s, 1970s, and 1980s, characterized by rapid uplift alternating with subsidence. The last unrest began in 2005 and is still ongoing, marked by ground uplift, increased seismicity, and high-flux gas emissions. The past and current unrest are matters of study and scientific debate. However, less attention has been dedicated to the subsidence phases, which, on the contrary, can give useful insights into the dynamics of the plumbing system. This study focuses on the subsidence phase following the '80 unrest and preceding the current unrest.  We present an unprecedented levelling dataset of hundreds of benchmarks measured with frequent campaigns. Data show a decreasing rate of subsidence velocity (max -1 m in Pozzuoli) and a normalized spatial pattern similar to the unrest phase. Geodetic modelling is conducted using the levelling time series, complemented by InSAR data from the ERS mission (1992--2003). A finite element model accounting for subsurface heterogeneity properties within the caldera is employed to analyze the deformation. By comparing these results with those from the current unrest phase, we assess whether the same two-source magmatic plumbing system, consisting of a shallower ellipsoid (4-6 km) and a deep sill (8 km) accounts for both subsidence and uplift phases. Understanding the mechanisms driving these contrasting deformation episodes is critical for interpreting the caldera's long-term dynamics and assessing future volcanic hazards.