Dynamics of the Neapolitan Volcanoes Inferred from Tiltmeter and Seismic Data Analysis: A Review

Abstract

We discuss some relevant results obtained in recent works on the Neapolitan Volcanoes, i.e., Campi Flegrei, Ischia, and Vesuvius (southern Italy) regarding the coupling between ground deformation detected by tiltmeters and volcano-tectonic seismicity. Great interest is devoted to those volcanoes because of the high level of volcanic risk, to which the inhabitants are exposed. Indeed, continuous and dense monitoring of their activity is provided by the Istituto Nazionale di Geofisica Vulcanologia, which employs different types of instrumentation, among which borehole tiltmeters and seismic networks. The works we consider in the present review focus on the link between seismicity and ground tilt anomalies covering the years 2015–2022. In detail, for the Campi Flegrei caldera, a significant variation in the tiltmeter pattern has been identified. Such anomaly indicates a transition to a different dynamical regime starting since 2020, also supported by some changes in the seismicity, ground temperatures of the fumarolic field, gravimetric and geochemical parameters. Concerning Ischia Island, a variation in the main tilt direction, which switched from NNW to NNE, has been detected in response to the Md 4.0 earthquake that occurred on 21 August 2017. Finally, at Vesuvius the relation among seismicity, ground inclination, and geochemical observables was investigated over the time interval 2012–2020 providing evidence of several simultaneous anomalies as proxies of the dynamical evolution of the volcanic system. Moreover, the comparison of the static displacement induced by seismicity with the measured tilt sheds light on the strict link between these two observables. The joint analyses of the seismic and tiltmeter signals represent a powerful tool for unraveling the volcanic dynamics and separating inner sources from external contributions.