Description: The causative source of the first damaging earthquake instrumentally recorded in the Island of Ischia, occurred on August 21 st 2017, has been studied through a multiparametric geophysical approach. In order to investigate the source geometry and kinematics we exploit seismological, GPS and Sentinel-1 and COSMO-SkyMed DInSAR co-seismic measurements. Our results indicate that the retrieved solutions from the geodetic data modelling and the seismological data are plausible; in particular, the best-fit solution consists of an E-W striking, south dipping normal fault, with its center located at a depth of 800 m. Moreover, the retrieved causative fault is consistent with the rheological stratification of the crust in this zone. This study allows us to improve the knowledge of the volcano-tectonic processes occurring on the Island, which is crucial for a better assessment of the seismic risk in the area.

Description: The Campi Flegrei caldera (CFc) is in an unrest phase, manifested by increasing ground uplift, seismicity and hydrothermal activity since 2005. The seismicity mainly involves the first 3 km below the main hydrothermal site of Solfatara-Pisciarelli. Geodetic data inversions generally localize the deformation source in this sector of the caldera. Two driving mechanisms of magmatic and non-magmatic unrest have been proposed. In this frame, investigating the physical properties of subsurface rocks can be valuable as they can largely affect local stress and strength, controlling volcano dynamics. We explored subsurface CFc rocks, extracted from 3-km-deep exploratory geothermal wells. X-ray microtomography investigations were combined with in-situ mechanical experiments (4D imaging) to characterize rock properties and link them with 3D microstructural changes. The cores, collected from the most representative stratigraphic levels, are dominated by tuffs alternating with minor lavas. The mineralogical assemblage reflects different depth-dependent T-P conditions ranging from argillic alteration (150 °C) to thermometamorphism (350 °C). Their tensile strength varies between 2 and 15 MPa and shows a general increase with depth, suggesting that similar excess pressures are required within a potential shallow chamber to drive magma transfer. Combining this data with correspondent elastic properties, it can be inferred that a volume change between 0.001 and 1 km〈sup〉3〈/sup〉 is sufficient to cause rupture conditions in a sill with radius between 0.5 and 5 km, respectively. These results are in agreement with magma volumes erupted during past eruptions at CFc, and particularly consistent with volcanological and petrological data of products from small-scale events.

Description: Between April 10th and May 22th 2006, a small seismic swarm of 5 volcano-tectonic events occurred on the volcanic island of Stromboli (Southern Italy). Two of these, having M 〉 3 and an intensity of about V-VI MCS, were clearly felt causing concern in the population. They were recorded during a period of increased explosive activity and were followed by two major explosions at the summit craters on May 22th, few hours after the last earthquake and on 16th June. The location of such events has been performed using a probabilistic approach based on the Equal Differential Time tecnique. Using this tecnique, we were able to locate all the events, showing how they cluster below the volcanic edifice at a depth of about 5÷6 km. From observed P wave polarities we determined the focal mechanisms of the 4 major events. Using earthquake scaling nlaws, we calculated the fault area and the average slip for the two major events. Finally, assuming an homogeneous half-space model we computed the isotropic stress changes below the volcano edifice. The negative stress variation over the central axis of the volcano suggests that the earthquakes were triggered by a pressurization of the magmatic system.

Description: Published

Description: open

Description: Stromboli is a volcanic island that is part of the Aeolian arch in the Mediterranean Sea (Italy). It is one of the most active volcanoes in Europe. Its moderate, but persistent, explosive activity makes it an ideal site for studies into the seismogenic processes in volcanic areas (Auger et al. 2006; Chouet et al. 2003; Chouet et al. 2008; D’Auria and Martini 2008; Del Pezzo et al. 1992; Esposito et al. 2008; Jaupart and Vergniolle 1989; Martini et al. 2007); it also attracts a lot of tourists. In the past, this combination of tourism and volcanic activity was not considered to be dangerous, but over the past few decades, Stromboli has produced stronger explosions that have in some cases injured people visiting the summit area. Moreover, in the recent history of Stromboli, two effusive eruptions have occurred that were accompanied by dangerous phenomena such as tsunami and vulcanian explosions. The first of these effusive eruptions (on 28 December 2002) produced a lava flow on the Sciara del Fuoco side, which is the northwest flank of the island. Two days later, a landslide occurred on this flank, which resulted in the propagation of a 10-m tsunami wave around the coasts of the island. These events demonstrate that Stromboli can be dangerous, even if its activity is not very energetic. Indeed, the Sciara del Fuoco structure is a weakness zone of the volcanic edifice that fractures when the explosive activity increases, giving rise to this effusive activity (Martini et al. 2007). Moreover, during the past two effusive eruptions, vulcanian explosions were associated with the end stages of the effusive phases. These damaged the village of Ginostra and caused fires in the vegetation. For these reasons, in January 2003, the Istituto Nazionale di Geofisica e Vulcanologia (INGV; the Italian National Institute of Geophysics and Volcanology) started to install a broadband seismic network that is designed to monitor Stromboli’s volcanic activity. This nature of the activity requires broadband instruments because the eruptive processes generate signals that span a wide range of frequencies (Chouet et al. 2003; Neuberg et al. 1994). At present, the typical seismic signals that are being recorded on Stromboli are: volcanic tremors with frequencies of 1–6 Hz; explosion quakes that include components with different frequency contents, ranging from some tens of seconds up to 10 Hz; long-period (LP) earthquakes with frequencies of 1–6 Hz; volcano-tectonic (VT) earthquakes with a frequency band of 1–20 Hz; and landslide signals with frequencies of 1–10 Hz. In particular, very long period (VLP) events with frequencies of 0.02–1 Hz are associated with the Strombolian explosions and represent the lower frequency content of the explosion quakes. Furthermore, the network records regional and teleseismic events.

Description: Published

Description: 435-439

Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive

Description: JCR Journal

Description: reserved

Description: Mt. Vesuvius (southern Italy) is one of the volcanoes that poses the greatest risk in the world because of its highly explosive eruptive style and its proximity to densely populated areas. The urbanization around Mt. Vesuvius began in ancient times, and the impact of eruptions on human activities has been severe. This is testified to by the ruins of Pompeii, which are covered by the products of the plinian eruption that took place in A.D. 79 (Sigurdsson et al. 1985), and more recently by the published reports of the eruptions that occurred from 1631 to 1944. For these reasons, Mt. Vesuvius was also one of the first volcanoes to be equipped with monitoring instruments. Pioneering instrumental observations began just before the second half of the 1800s, when the Vesuvius Observatory was founded in 1841 (Imbò 1949). At that time, Vesuvius was very active (Ricciardi 2009), and its effusive and explosive eruptions often caused damage to the surrounding areas. At the same time, it was a famous tourist attraction that drew travelers from all over the world (Gasparini and Musella 1991). Since the middle of the 1800s, at least 12 eruptions have occurred that have been superimposed on persistent intra-crater activity that has been characterized by Strombolian explosions and by the formation of small lava lakes. The last eruption occurred on 18 March 1944 and marked a change in the status of Mt. Vesuvius, as it entered a closed-conduit phase that persists today. Following this last eruption, a change occurred in the 1960s, as documented by an increase in the occurrence rate of earthquakes. Since 1972, the monitoring of Mt. Vesuvius has improved over time and become more systematic, so that there is a remarkable dataset relating to the current phase of quiescence. Over more than a century and a half of observations, many monitoring instruments have been used for Mt. Vesuvius, including early seismometers, several of which are now kept in the Museum of Volcanology of the Vesuvius Observatory. The present monitoring system is based on seismological, geodetical geodetical, and geochemical observations performed using an instrumental network that was designed on the basis of the current state of the volcano while also taking into account the likely scenario of future unrest.

Description: Published

Description: 625-634

Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive

Description: JCR Journal

Description: reserved

Description: Mt. Vesuvius (southern Italy) is one of the volcanoes with the greatest risk in the World because of its highly explosive eruptive style and its proximity to densely populated areas. The urbanization around Mt. Vesuvius began in ancient times and the impact of eruptions on human activities has been very hard...

Description: INGV,sezione di Napoli,Osservatorio Vesuviano

Description: Published

Description: Tenerife, Canary Islands, Spain

Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive

Description: open

Description: L’Italia e l’Indonesia hanno avviato nel 2005-2006 un progetto di cooperazione sulle tematiche della mitigazione del rischio vulcanico. Nell’ambito di questo progetto è stata individuata la zona ovest di Sumatra come area di intervento. In particolare è stato preso in considerazione il vulcanoMarapi. Questo vulcano ha avuto frequente attività eruttiva nelle ultime decine di anni. L’ultima eruzione si è verificata nel 2004. La sua attività, sebbene di moderata intensità, pone un problema di protezione civile, poiché dal 1980 ad oggi ha causato diversi feriti e alcune vittime tra i turisti che hanno visitato l’area craterica sommitale. Allo scopo di monitorare lo stato di attività del Marapi, nell’ambito del citato progetto è stata realizzata una rete sismica a larga banda composta da 4 stazioni e basata su sensori Guralp GMG-40T da 60s di periodo e su acquisitori di tipo GAIA2, prodotti presso l’Istituto Nazionale di Geofisica e Vulcanologia. La strumentazione è stata portata dall’Italia ed è stata installata da un gruppo di lavoro formato da italiani ed indonesiani. Oltre all’installazione della strumentazione in campagna è stato necessario allestire un vero e proprio Centro di Monitoraggio presso l’Osservatorio di Bukittinggi, in prossimità delle pendici nordoccidentali del vulcano, dotato di calcolatori per l’acquisizione, l’analisi dei dati e la loro archiviazione. Il sistema per ilmonitoraggio sismologico realizzato alMarapi costituisce un importante strumento di prevenzione del rischio associato all’attività di questo vulcano e sta permettendo di creare un ricco data set utile a caratterizzare la sismicità della struttura vulcanica e dell’area circostante. Da un’analisi preliminare dei dati registrati nel periodo 19/10/2006 - 24/11/2008 si evidenzia che il vulcanomanifesta una sismicità di tipo VT ed LP. Nell’ agosto 2007 sono stati inoltre registrati segnali probabilmente attribuibili a modesta attività esplosiva nell’area sommitale. Italy and Indonesia started a cooperation project in 2005-2006 to cover issues for the mitigation of volcanic risk. In this project, the west area of Sumatra was identified as the area for intervention. In particular, the Marapi volcano was considered. This volcano has shown frequent eruptive activity over recent decades, with the last eruption occurring in 2004. Although its activity is of moderate intensity, it creates a civil protection problem, because since 1980 it has resulted in several injuries and a number of deaths among the tourists who visit the summit crater area. To monitor the activity of Marapi volcano as part of this project, a broadband seismic network has been implemented that consists of four stations based on Guralp GMG 40T sensors with period of 60 s and on GAIA2 data-loggers, which are produced at the INGV. The instrumentation was brought from Italy and was installed by a working group comprising Italians and Indonesians. In addition to the instrumentation in the field, it was necessary to set up a monitoring centre in the Bukittinggi Observatory, which is near the north-western slopes of the Marapi volcano. This is equipped with computers for data acquisition, analysis and archiving. The system for seismological monitoring that has been realized atMarapi volcano is an important tool in the prevention of the risk associated with this volcano, and it is providing a rich dataset that will be of great use for the characterization of the seismicity of the Marapi volcanic structure and the surrounding area. A preliminary analysis of the data recorded during the period 19/10/2006 - 24/11/2008 evidences that the volcano shows VT and LP seismicity. In August 2007 were also recorded signals probably attributable to small explosive activity in the summit area.

Description: INGV Istituto Nazionale di Geofisica e Vulcanologia

Description: Published

Description: 5-21

Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive

Description: N/A or not JCR

Description: open

Description: Seismic monitoring of active volcanoes has different and sometimes contrasting requirements. The peculiar features of volcanic seismicity makes an interactive system more complex than required for typical seismic monitoring. Intense seismic swarms of small magnitude earthquakes need a rapid but consistent processing for tracking in real time the evolution of an ongoing volcanic unrest. At the same time a comparison with the past record for detecting patterns still observed or anomalous behaviours is needed. Furthermore a correlation between different parameters as event magnitude and depth, event occurrence rate and volcanic tremor amplitude may be required. Finally, a rapid exchange of information among scientists located worldwide can be important for drawing conclusions about the evolution of a crisis. The first task can be fullfilled by an automatic seismic processing system, followed by a manual revision from expert seismologists. The second and the third can be simply accomplished storing the results of the processing in relational databases, that very well suited for such applications. The last task can be simply achieved by making the dataset accessible on-line thour a web server, in a friendly and interactive way. On the basis of the experience matured on the automatic seismic monitoring system of Stromboli ([2]) the research team of Monitoring Centre of I.N.G.V. “Osservatorio Vesuviano” started developing a similar software infrastructure for the monitoring of Neapolitan volcanoes. The existing databases: GeoVes, with supervised analysis, and Web Based Seismological Monitoring (WBSM) system, with automatic location, have been joined into a single friendly graphical interface aimed at improving the data accesibility and efficiency of the monitoring system.

Description: Published

Description: 363-374

Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive

Description: 5.9. TTC - Sistema web

Description: open

Description: Obiettivo principale del monitoraggio dei vulcani attivi è individuare e misurare fenomeni che possono essere indotti dal movimento del magma in profondità. Dal punto di vista sismologico questi fenomeni possono essere sciami sismici, eventi a bassa frequenza, microtremore vulcanico ed eventi very long period (VLP). Attraverso la misura, l'analisi e la corretta interpretazione di questi fenomeni è possibile capire in anticipo se un vulcano sta evolvendo verso una ripresa dell'attività eruttiva. L'Osservatorio Vesuviano - INGV ha tra i suoi compiti istituzionali il monitoraggio del Vesuvio, dei Campi Flegrei e di Ischia che sono, come è noto, vulcani a alto rischio a causa del loro stile eruttivo prevalentemente esplosivo e della presenza nelle loro prossimità di vaste aree urbanizzate. Per effettuare il monitoraggio sismologico di dette aree l'Osservatorio Vesuviano ha sviluppato e mantiene una rete che trasmette i dati in continuo al centro di sorveglianza. La configurazione attuale della rete comprende 28 stazioni analogiche a corto periodo (1Hz) e 4 stazioni digitali a larga banda.

Description: Published

Description: Roma

Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive

Description: open

Description: On February 27, 2007, the Stromboli volcano, which has usually been characterized by moderate explosive activity, started an effusive eruption with a small lava flow down the NW flank. The permanent broadband network installed on the island allowed the revealing of anomalies in the seismicity before the effusive eruption and for the phenomena to be followed over time, thus obtaining meaningful information about the eruption dynamics. During the effusive phase, a major explosion occurred on March 15, 2007. On that occasion, two strainmeters deployed on the volcano in the previous year recorded a strain increment before the blast. After this explosion, which further destabilized the upper part of the edifice, swarms of Long-Period (LP) and hybrid events were recorded. The characteristics and locations of these events suggest that they were associated with the fracturing processes that affected the summit area of the cone. During the effusive phase, changes in the Very Long Period (VLP) event location were recorded. This type of events accompanied the change in the eruptive style, providing information about the magmatic conduit involved in their seismogenetic processes. The effusive phase stopped on April 2, 2007, and the typical Strombolian activity restarted some months later.

Description: JCR Journal

Description: open