Scarpato, Giovanni

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 (Mw < 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.

Two paroxysmal explosions occurred at Stromboli on July 3 and August 28, 2019, the first of which caused the death of a young tourist. After the first paroxysm an effusive activity began from the summit vents and affected the NW flank of the island for the entire period between the two paroxysms. We carried out an unsupervised analysis of seismic and infrasonic data of Strombolian explosions over 10 months (15 November 2018–15 September 2019) using a Self- Organizing Map (SOM) neural network to recognize changes in the eruptive patterns of Stromboli that preceded the paroxysms. We used a dataset of 14,289 events. The SOM analysis identified three main clusters that showed different occurrences with time indicating a clear change in Stromboli’s eruptive style before the paroxysm of 3 July 2019. We compared the main clusters with the recordings of the fixed monitoring cameras and with the Ground-Based Interferometric Synthetic Aperture Radar measurements, and found that the clusters are associated with different types of Strombolian explosions and different deformation patterns of the summit area. Our findings provide new insights into Strombolian eruptive mechanisms and new perspectives to improve the monitoring of Stromboli and other open conduit volcanoes.

In the context of recent developments in volcanic muography, we describe an experiment at Vesuvius, the volcano near Naples that destroyed Pompeii and Herculaneum (Italy) in 79 AD. This volcano is about 1200\,m high with a typical summit caldera formed by Mount Somma. Vesuvius is among the highest-risk volcanoes in the world due to its highly explosive eruptive style and the high population density of the area where it is located. Volcanoes are generally fragile geological structures, prone to produce partial collapse and large landslides that can affect the style of eruptions. Moreover, the knowledge of the internal structure is fundamental for understanding past eruption activity and for constraining eruption models. For these reasons, studying the internal structure of the ``Gran Cono'' (great cone) of Vesuvius and the physical characteristics of its rock is important and led us to design a muography experiment at Vesuvius. This experiment, which is currently in progress, is based on three scintillator detectors with a surface of 1\,m$^2$ each. These detector features have been implemented to overcome the problems related to the large thickness of rock that form the ``Gran Cono'' of Vesuvius and the effects that can be a source of error in data processing. These aspects represent an open challenge for the muography of large volcanoes, which today constitutes the frontier of research in the field of volcanic muography.

We present the main features of the permanent monitoring system managed by the Istituto Nazionale di Geofisica e Vulcanologia-Osservatorio Vesuviano in the Campi Flegrei caldera. Eruptive history of this active volcano shows that the majority of the eruptive events has been characterised by high explosivity and was accompanied by pyroclastic density currents. Its last eruption occurred in AD 1538 and in the next centuries the Campi Flegrei caldera has experienced several episodes of bradyseism and also the progressive increasing of the urbanisation in the area (west of Naples). Monitoring the dynamics of a mainly explosive volcano completely embedded in a very populated area is a challenging task. In order to detect any variation in the physical and chemical parameters of the Campi Flegrei caldera, the Istituto Nazionale di Geofisica e Vulcanologia-Osservatorio Vesuviano manages a permanent multi-parametric monitoring system. All the recorded h24 continuous data are transmitted to the Monitoring Room of the Osservatorio Vesuviano in Naples, where they are acquired, processed and evaluated to define changes in the dynamical state of the volcano. The caldera, since the end of 2004, is experiencing a bradyseismic episode characterised by a low velocity rate uplift, low energy earthquakes and increasing in the magmatic components of fumarolic fluids. The monitoring and surveillance activity of the Campi Flegrei caldera plays a crucial role in the volcanic emergency plan that includes evacuation of approximately 500,000 people before the beginning of the eruption.

The MURAVES experiment aims at the muographic imaging of the internal structure of the summit of Mt. Vesuvius, exploiting muons produced by cosmic rays. Though presently quiescent, the volcano carries a dramatic hazard in its highly populated surroundings. The challenging measurement of the rock density distribution in its summit by muography, in conjunction with data from other geophysical techniques, can help the modeling of possible eruptive dynamics. The MURAVES apparatus consists of an array of three independent and identical muon trackers, with a total sensitive area of 3 square meters. In each tracker, a sequence of 4 XY tracking planes made of plastic scintillators is complemented by a 60 cm thick lead wall inserted between the two downstream planes to improve rejection of background from low-energy muons. The apparatus is currently acquiring data. Preliminary results from the analysis of the first data sample are presented.

L'Istituto Nazionale di Geofisica e Vulcanologia (INGV) è componente del Servizio Nazionale di Protezione Civile, ex articolo 6 della legge 24 febbraio 1992 n. 225 ed è Centro di Competenza per i fenomeni sismici, vulcanici e i maremoti per il Dipartimento della Protezione Civile Nazionale (DPC). L’Osservatorio Vesuviano, Sezione di Napoli dell’INGV, ha nei suoi compiti il monitoraggio e la sorveglianza H24/7 delle aree vulcaniche attive campane (Vesuvio, Campi Flegrei e Ischia). Tali attività sono disciplinate dall’Accordo-Quadro (AQ) sottoscritto tra il DPC e l’INGV per il decennio 2012-2021 e sono dettagliate negli Allegati A e B del suddetto AQ. Il presente Rapporto sul Monitoraggio dei Vulcani Campani rappresenta l’attività svolta dall’Osservatorio Vesuviano e dalle altre Sezioni INGV impegnate nel monitoraggio dell’area vulcanica campana nel secondo semestre 2019.

The Istituto Nazionale di Geofisica e Vulcanologia (INGV) is an Italian research institution with focus on earth sciences. Moreover, the INGV is the operational center for seismic surveillance and earthquake monitoring in Italy and is a part of the civil protection system as a center of expertise on seismic, volcanic, and tsunami risks.INGV operates the Italian National Seismic Network and other networks at national scale and is a primary node of the European Integrated Data Archive for archiving and distributing strong‐motion and weak‐motion seismic recordings. In the control room in Rome, INGV staff performs seismic surveillance and tsunami warning services; in Catania and Naples, the control rooms are devoted to volcanic surveillance. Volcano monitoring includes locating earthquakes in the regions around the Sicilian (Etna, Eolian Islands, and Pantelleria) and the Campanian (Vesuvius, Campi Fregrei, and Ischia) active volcanoes. The tsunami warning is based on earthquake location and magnitude (M) evaluation for moderate to large events in the Mediterranean region and also around the world. The technologists of the institute tuned the data acquisition system to accomplish, in near real time, automatic earthquake detection, hypocenter and magnitude determination, and evaluation of several seismological products (e.g., moment tensors and ShakeMaps). Database archiving of all parametric results is closely linked to the existing procedures of the INGV seismic surveillance environment and surveillance procedures. Earthquake information is routinely revised by the analysts of the Italian seismic bulletin. INGV provides earthquake information to the Department of Civil Protection (Dipartimento di Protezione Civile) to the scientific community and to the public through the web and social media. We aim at illustrating different aspects of earthquake monitoring at INGV: (1) network operations; (2) organizational structure and the hardware and software used; and (3) communication, including recent developments and planned improvements.

L'Istituto Nazionale di Geofisica e Vulcanologia (INGV) è componente del Servizio Nazionale di Protezione Civile, ex articolo 6 della legge 24 febbraio 1992 n. 225 ed è Centro di Competenza per i fenomeni sismici, vulcanici e i maremoti per il Dipartimento della Protezione Civile Nazionale (DPC). L’Osservatorio Vesuviano, Sezione di Napoli dell’INGV, ha nei suoi compiti il monitoraggio e la sorveglianza H24/7 delle aree vulcaniche attive campane (Vesuvio, Campi Flegrei e Ischia). Tali attività sono disciplinate dall’Accordo-Quadro (AQ) sottoscritto tra il DPC e l’INGV per il decennio 2012-2021 e sono dettagliate negli Allegati A e B del suddetto AQ. Il presente Rapporto sul Monitoraggio dei Vulcani Campani rappresenta l’attività svolta dall’Osservatorio Vesuviano e dalle altre Sezioni INGV impegnate nel monitoraggio dell’area vulcanica campana nel primo semestre 2019.

The Neapolitan volcanic area includes three active and high-risk volcanoes: Campi Flegrei caldera, Somma–Vesuvius, and Ischia island. The Campi Flegrei volcanic area is a typical example of a resurgent caldera, characterized by intense uplift periods followed by subsidence phases (bradyseism). After about 21 years of subsidence following the 1982–1984 unrest, a new inflation period started in 2005 and, with increasing rates over time, is ongoing. The overall uplift from 2005 to December 2019 is about 65 cm. This paper provides the history of the recent Campi Flegrei caldera unrest and an overview of the ground deformation patterns of the Somma–Vesuvius and Ischia volcanoes from continuous GPS observations. In the 2000–2019 time span, the GPS time series allowed the continuous and accurate tracking of ground and seafloor deformation of the whole volcanic area. With the aim of improving the research on volcano dynamics and hazard assessment, the full dataset of the GPS time series from the Neapolitan volcanic area from January 2000 to December 2019 is presented and made available to the scientific community

Studying seismicity in a volcanic environment provides important information on the state of activity of volcanoes. The seismicity of the Neapolitan volcanoes, Campi Flegrei, Vesuvius, and Ischia, shows distinctive characteristics for each volcano, coveringwide range of patterns and types. In this study we relocated some significant volcano- tectonic earthquake swarms that occurred in Campi Flegrei and Vesuvius. Moreover, we compared the earthquake occurrence evolution, the magnitude and the seismic energy release of the three volcanoes. Also, we considered the results of seismic analysis in the light of geochemical and ground deformation data that contribute to defining the state of activity of volcanoes. In Campi Flegrei, which is experiencing a long term unrest, we identified a seismogenic structure at shallow depth in Pisciarelli zone that has been activated repeatedly. The increasing seismicity accompanies an escalation of the hydrothermal activity and a ground uplift phase. At Vesuvius a very shallow seismicity is recorded, which in recent years has shown an increase in terms of the number of events per year. Earthquakes are usually located right beneath the crater axis. They are concentrated in a volume affected by the hydrothermal system. Finally, Ischia generally shows a low level of seismicity, however, in Casamicciola area events with a moderate magnitude can occur and these are potentially capable of causing severe damage to the town and population, due to their small hypocentral depth (typically < 2.5 km). After the seismic crisis of August 21, 2017 (mainshock magnitude M 4), the seismicity returned to a low level in terms of occurrence rate and magnitude of earthquakes. The seismicity of these three different volcanic areas shows some common aspects that highlight a relevant role of hydrothermal processes in the seismogenesis of volcanic areas. However, while the main swarms in Campi Flegrei and most of the Vesuvian earthquakes are distributed along conduit-like structures, the seismicity of Ischia is mainly located along faults. Furthermore, the temporal evolution of seismicity in Neapolitan volcanic area suggests a concomitant increase in the occurrence of earthquakes both in Campi Flegrei and Vesuvius in recent years.