Modeling of volcanic sources and evolution of stress and strain rate at Campi Flegrei caldera (Italy) from GNSS data (2000-2022)

Abstract

The Campi Flegrei caldera (southern Italy) is one of the most populated volcanic areas on the Earth. It is characterized by intense uplift episodes followed by subsidence phases. Following the 1982–1984 unrest, there was about 21 years of subsidence,  followed by a new phase of inflation started in 2005 and, with increasing uplift rates over time, is still ongoing. Since 2005, the total vertical ground displacement is about 1 m near the city of Pozzuoli.We analyze the evolution of the volcanic sources that caused the measured ground deformations since 2000 by modelling the Global Navigation Satellite System (GNSS) data from the permanent monitoring network in the caldera. Based on changes in slope in the GNSS displacement time series, we divide the recent inflation period into different phases. During time periods characterized by a near-linear trend, we can infer that a stationary pressure source is active inside the caldera. Using this inference, we describe the ground deformations of the last two decades through different sub-intervals, as “snapshots” that are the result of the time evolution of the inner volcano-dynamics.Furthermore, over the investigated period we analyze the evolution of surface stresses from an ellipsoidal source model and the strain rate patterns from the horizontal GNSS velocities. In particular, we compute areal strain rates, shear strain rate magnitudes, associated with a strike-slip component of deformation, and rotation rates, and this helps us to infer surface manifestations of subsurface deformations.