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The Hunga Tonga-Hunga Ha’apai volcano (Pacific Ocean) generated a cataclysmic explosion on 15 January 2022, triggering several atmospheric disturbances at a global scale, as a huge increase in the total electron content (TEC) in the ionosphere, and a pressure wave travelling in the troposphere. We collected and analysed data over the Mediterranean to study these disturbances, and in particular, (i) data from the barometric and infrasonic stations installed on Italian active volcanoes by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) for investigating the tropospheric pressure waves; (ii) barometric data from the INGV-TROPOMAG and SIAS (Sicilian Agro-meteorological Information System) networks, for investigating the interaction between the orography and pressure waves; (iii) ionograms from the Advanced Ionospheric Sounder-INGV ionosonde at Gibilmanna (Sicily, Italy); (iv) data from the RING (Rete Italiana Integrata GNSS) network, to retrieve the ionospheric TEC; (v) soil CO2 flux data from the INGV surveillance network of Vulcano Island. The analysis of the ground-level barometric data highlights that pressure waves were reflected and diffracted by the topographic surface, creating a complex space–time dynamic of the atmospheric disturbances travelling over Sicily, driven by the interference among the different wavefronts. The ionograms show that a medium-scale travelling ionospheric disturbance (MSTID), with a horizontal wavelength of about 220 km and a period of about 35 min, propagated through the ionospheric plasma in the correspondence of the first barometric variations. Moreover, comparing detrended TEC and barometric data, we further confirmed the presence of the aforementioned MSTID together with its close relation to the tropospheric disturbance.

The volcanic island of Ischia has shown to have an important seismogenic potential, being the location of several destructive earthquakes, e.g. 1881, 1883 and 2017. The damage caused by these earthquakes was more connected to the proximity of the source to the surface than to their magnitude (M w < 5.2). The need to monitor and model this seismicity required the installation of a dense and modern seismic network. The first modern seismic station on the island was installed in 1993, and the network was successively increased with time. A meaningful improvement to the network was made after the earthquake that occurred on the 21 of August 2017. The network currently has 11 sites with velocimeters and some of them with accelerometers installed too. We analysed the seismic network configuration in comparison with the seismicity that characterizes the area to mark a starting point for future seismological analysis. The network is currently able to locate shallow earthquakes with duration magnitude greater or equal to 0 in the whole island.

Hydrothermal activity is a natural manifestation of volcanic degassing at calderas, testified by the presence of fumarolic fields, boiling pools, steaming ground and soil diffuse degassing, which are of interest for volcano monitoring and surveillance as they can be related to the magma dynamics within the caldera reservoirs. Campi Flegrei (Italy) is a half submerged resurgent caldera with a nested structure located at the western edge of the bay of Naples. Since its last eruption in 1538, several episodes of ground uplift accompanied by seismic swarms and intense degassing have been reported. The last uplift phase started in 2005 and is still ongoing. The Pisciarelli fumarolic field is a key area of the Campi Flegrei caldera where a continuous and vigorous degassing of hydrothermal fluids, of magmatic origin, takes place. Such fumarolic degassing is associated with a persistent harmonic tremor showing within the last decade an increasing amplitude trend that correlates well with the geochemical and geodetic unrest indicators of the caldera. In the framework of the DPC-INGV 2012-2021 Agreement and the LOVE-CF Project, we investigated the seismo-acoustic wavefield produced by fumarolic degassing with the aim of characterizing the source process that produces the harmonic tremor, and to propose a potential seismo-acoustic based tool to estimate the fumarolic gas fluxes in real time. At this aim, we performed a series of temporary geophysical experiments with the deployment of 4-element small aperture seismo-acoustic arrays equipped, at each array element, by a short-period three-component seismometer and a broadband infrasonic pressure sensor. We show that the harmonic tremor source is located within the fumarolic field at shallow depth (