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  • 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
  • Springer  (11)
  • Elsevier Science Limited  (10)
  • Lower Hutt : Institute of Geological and Nuclear Sciences
  • Nature Publishing Group
Collection
Keywords
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  • 1
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    Time-dependent Coulomb stress changes induced by the 2002-2003 Etna magmatic intrusions and implications on following seismic activities (2016)
    Elsevier Science Limited
    Details
    Publication Date: 2021-06-25
    Description: In this paper, the relationship between the dike-forming magmatic intrusions and the faulting process at Mount Etna is investigated in terms of Coulomb stress changes. As case study, a complete time-dependent 3-D finite element model for the 2002-2003 eruption at Mount Etna is presented. In the model, which takes into account the topography, medium heterogeneities and principal fault systems in a viscoelastic/plastic rheology, we sequentially activated three dike-forming processes and looked at the induced temporal evolution of the Coulomb stress changes, during the co-intrusive and post-intrusive periods, on Pernicana and Santa Venerina faults. We investigated where and when fault slips were encouraged or not, and consequently how earthquakes may have been triggered. Results show positive Coulomb stress changes for the Pernicana Fault in accordance to the time, location and depth of the 27th October 2002 Pernicana earthquake (Md = 3.5). The amount of Coulomb stress changes in the area of Santa Venerina Fault, as induced by dike-forming intrusions only, is instead almost negligible and, probably, not sufficient to trigger the 29th October Santa Venerina earthquake (Md = 4.4), occurred two days after the start of the eruption. The necessary Coulomb stress change value to trigger this earthquake is instead reached if we consider it as induced by the 27th October Pernicana biggest earthquake, combined with the dike-induced stresses.
    Description: MED-SUV FP7 Project (Grant number 308665)
    Description: Published
    Description: 185-196
    Description: 4V. Dinamica dei processi pre-eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Coulomb stress changes ; Finite Element Model ; Viscoelasticity ; Earthquakes ; Mount Etna ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.03. Geodesy::04.03.07. Satellite geodesy ; 04. Solid Earth::04.03. Geodesy::04.03.08. Theory and Models ; 04. Solid Earth::04.06. Seismology::04.06.02. Earthquake interactions and probability ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk ; 05. General::05.01. Computational geophysics::05.01.03. Inverse methods
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Seismic footprints of shallow dyke propagation at Etna, Italy (2016)
    Nature Publishing Group
    Details
    Publication Date: 2017-04-04
    Description: One of the key issues in forecasting volcanic eruptions is to detect signals that can track the propagation of dykes towards the surface. Continuous monitoring of active volcanoes helps significantly in achieving this goal. The seismic data presented here are unique, as they document surface faulting processes close (tens to a few hundred meters) to their source, namely the dyke tip. They originated nearby - and under - a seismic station that was subsequently destroyed by lava flows during eruptive activity at Etna volcano, Italy, in 2013. On February 20, a ~600 m-long and ~120 m wide NW-SE fracture field opened at an altitude between 2750 and 2900 m. The consequent rock dislocation caused the station to tilt and offset the seismic signal temporarily. Data acquisition continued until the arrival of the lava flow that led to the breakdown of the transmission system. Shallow ground fracturing and repeated low-frequency oscillations occurred during two stages in which the seismic signal underwent a maximum offset ~2.57 E+04 nm/s. Bridging instrumental recordings, fieldwork and conceptual modelling, these data are interpreted as the seismic footprints of a magmatic dyke intrusion that moved at speed ~0.02 m/s (first stage) and 0.46 m/s (second stage).
    Description: This work was supported by the MED-SUV project, which has received funding from the European Union’s Seventh Programme for research, technological development and demonstration under grant agreement No 308665.
    Description: Published
    Description: 11908
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: dyke propagation ; Etna ; seismic signals ; ground fracturing ; conceptual modelling ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    Viscous plugging can enhance and modulate explosivity of strombolian eruptions (2015)
    Elsevier Science Limited
    Details
    Publication Date: 2021-03-01
    Description: Strombolian activity is common in low-viscosity volcanism. It is characterised by quasi-periodic, short-lived explosions, which, whilst typically weak, may vary greatly in magnitude. The current paradigm for a strombolian volcanic eruption postulates a large gas bubble (slug) bursting explosively after ascending a conduit filled with low-viscosity magma. However, recent studies of pyroclast textures suggest the formation of a region of cooler, degassed, more-viscous magma at the top of the conduit is a common feature of strombolian eruptions. Following the hypothesis that such a rheological impedance could act as a ‘viscous plug’, which modifies and complicates gas escape processes, we conduct the first experimental investigation of this scenario. We find that: 1) the presence of a viscous plug enhances slug burst vigour; 2) experiments that include a viscous plug reproduce, and offer an explanation for, key phenomena observed in natural strombolian eruptions; 3) the presence and extent of the plug must be considered for the interpretation of infrasonic measurements of strombolian eruptions. Our scaled analogue experiments show that, as the gas slug expands on ascent, it forces the underlying low-viscosity liquid into the plug, creating a low-viscosity channel within a high-viscosity annulus. The slug's diameter and ascent rate change as it enters the channel, generating instabilities and increasing slug overpressure. When the slug reaches the surface, a more energetic burst process is observed than would be the case for a slug rising through the low-viscosity liquid alone. Fluid-dynamic instabilities cause low and high viscosity magma analogues to intermingle, and cause the burst to become pulsatory. The observed phenomena are reproduced by numerical fluid dynamic simulations at the volcanic scale, and provide a plausible explanation for pulsations, and the ejection of mingled pyroclasts, observed at Stromboli and elsewhere.
    Description: European Union’s Seventh Framework Programme (FP7/2007–2013) project NEMOH, REA grant agreement No. 289976
    Description: Published
    Description: 210-218
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: analogue modeling ; strombolian explosions ; plugged vents ; volcano acoustic ; volcano infrasonic ; slug bursting ; Taylor bubble ; 04. Solid Earth::04.03. Geodesy::04.03.06. Measurements and monitoring ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
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    Dynamics of mild strombolian activity on Mt. Etna (2015)
    Elsevier Science Limited
    Details
    Publication Date: 2021-05-12
    Description: Here we report the first measurements of gas masses released during a rare period of strombolian activity at the Bocca Nuova crater, Mt. Etna, Sicily. UV camera data acquired for 195 events over an ≈27 minute period (27th July 2012) indicate erupted SO2 masses ranging from ≈0.1 to ≈14 kg per event, with corresponding total gas masses of ≈0.1 to 74 kg. Thus, the activity was characterised by more frequent and smaller events than typically associated with strombolian activity on volcanoes such as Stromboli. Events releasing larger measured gas masses were followed by relatively long repose periods before the following burst, a feature not previously reported on from gas measurement data. If we assume that gas transport within the magma can be represented by a train of rising gas pockets or slugs, then the high frequency of events indicates that these slugs must have been in close proximity. In this case the longer repose durations associated with the larger slugs would be consistent with interactions between adjacent slugs leading to coalescence, a process expedited close to the surface by rapid slug expansion. We apply basic modelling considerations to the measured gas masses in order to investigate potential slug characteristics governing the observed activity.We also cross correlated the acquired gas fluxes with contemporaneously obtained seismic data but found no relationship between the series in line with the mild form of manifest explosivity.
    Description: Published
    Description: 103–111
    Description: 3V. Dinamiche e scenari eruttivi
    Description: JCR Journal
    Description: open
    Keywords: Mild strombolian activity ; Ultra-violet imaging ; Volcanic gas measurements ; Slug dynamics ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
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    Tectonic stress and renewed uplift at Campi Flegrei caldera, southern Italy: New insights from caldera drilling (2015)
    Elsevier Science Limited
    Details
    Publication Date: 2020-05-29
    Description: Deep drilling is a key tool for the investigation of active volcanoes in the modern Earth Sciences, as this provides the only means to obtain direct information on processes that occur at depth. Data acquired from drilling projects are fundamental to our understanding of volcano dynamics, and for mitigation of the hazards they pose for millions of people who live close to active volcanoes. We present here the first borehole measurement of the stress field in the crust of Campi Flegrei (southern Italy), a large active caldera, and one of the highest risk volcanoes worldwide. Measurements were performed to depths of ∼500m during a pilot study for the Campi Flegrei Deep Drilling Project. These data indicate an extensional stress field, with a minimum horizontal stress of ca. 75% to 80% of the maximum horizontal stress, which is approximately equal to the vertical stress. The deviation from lithostatic conditions is consistent with a progressive increase in applied horizontal stress during episodes of unrest, since at least 1969. As the stress field is evolving with time, the outcome of renewed unrest cannot be assessed by analogy with previous episodes. Interpretations of future unrest must therefore accommodate the possibility that Campi Flegrei is approaching conditions that are more favourable to a volcanic eruption than has previously been the case. Such long-term accumulation of stress is not expected to be unique to Campi Flegrei, and so might provide a basis for improved forecasts of eruptions at large calderas elsewhere.
    Description: Published
    Description: 23-29
    Description: 6T. Sismicità indotta e caratterizzazione sismica dei sistemi naturali
    Description: 4V. Vulcani e ambiente
    Description: 5A. Energia e georisorse
    Description: 7A. Geofisica di esplorazione
    Description: JCR Journal
    Description: restricted
    Keywords: Campi Flegrei ; stress ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    Long-period seismicity at Shishaldin volcano (Alaska) in 2003–2004: Indications of an upward migration of the source before a minor eruption (2015)
    Elsevier Science Limited
    Details
    Publication Date: 2017-04-04
    Description: We have analyzed the long-period (LP) seismic activity at Shishaldin volcano (Aleutians Islands, Alaska) in the period October 2003–July 2004, during which a minor eruption took place in May 2004, with ash and steam emissions, thermal anomalies, volcanic tremor and small explosions. We have focused the attention on the time evolution of LP rate, size, spectra and polarization dip angle along the dataset. We find an evolution toward more shallow dip angles in the polarization of the waveforms during the sequence. The dip angle is a manifestation of the source location. Because the LP seismic sources are presumed to reflect the aggregation of gas slug or pockets within the melt, we use the polarization dip at the LP onset as a proxy for the nucleation depth of the seismic events within the conduit. We refer to this parameter as the nucleation dip and the position along the conduit of the gas aggregation as nucleation depth. The nucleation dip changes throughout the dataset. It shows a sharp decrease between the end of December 2003 and the end of January 2004, followed by a gradual increase until the onset of the eruption. At the same time, a general increase of the LP rate occurs. We have associated the dip evolution with a sinking and a subsequent decrease of the nucleation depth, which would quickly migrate up to about 8 km below the crater rim, followed by a slow depth decrease which culminates in the eruption. The change in the nucleation depth reflects either a pressure variationwithin the plumbing system,whichwould affect the confining pressure experienced by the gas aggregations. We have imputed such a pressure change to the intrusion of batches of magma from a deeper magma chamber (b10 km) toward a shallower one (N5 km). For a cylindric conduit with rigid walls, this leads to a volume of the injected new magma of 105–107 m3, compatible with estimates in other areas, suggesting that the LP process can be considered a good proxy of the thermodynamical conditions of the shallow plumbing system.
    Description: Published
    Description: 14–24
    Description: 4T. Fisica dei terremoti e scenari cosismici
    Description: JCR Journal
    Description: restricted
    Keywords: Shishaldin volcano ; Long-period events ; Polarization ; Eruption precursors ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    SO2 flux monitoring at Stromboli with the new permanent INGV SO2 camera system: A comparison with the FLAME network and seismological data (2015)
    Elsevier Science Limited
    Details
    Publication Date: 2017-04-04
    Description: We installed a permanent SO2 camera system on Stromboli, Italy, in May 2013, in order to improve our capacity to monitor the SO2 emissions from this volcano. The camera collects images of SO2 concentrations with a period of ~ 10 s, allowing quantification of short-term processes, such as the gas released during the frequent explosions which are synonymous with Stromboli. It also allows quantification of the quiescent gas flux, and therefore comparison with the FLAME network of scanning ultraviolet spectrometers previously installed on the island. Analysis of results from the SO2 camera demonstrated a good agreement with the FLAME network when the plume was blown fully into the field of view of the camera. Permanent volcano monitoring with SO2 cameras is still very much in its infancy, and therefore this finding is a significant step in the use of such cameras for monitoring, whilst also highlighting the requirement of a favourable wind direction and strength. We found that the explosion gas emissions are correlated with seismic events which have a very long period component. There is a variable time lag between event onset time and the increase in gas flux observed by the camera as the explosion gas advects into the field of view of the camera. This variable lag is related to the plume direction, as shown by comparison with the plume location detected with the FLAME network. The correlation between explosion gas emissions and seismic signal amplitude show is consistent with a gas slug-driven mechanism for seismic event production. Comparison of the SO2 camera measurements of the quiescent gas flux shows a fair quantitative agreement with the SO2 flux measured with the FLAME network. Overall, the SO2 camera complements the FLAME network well, as it allows frequent quantification of the explosion gas flux produced by Stromboli, whose signal is in general too brief to be measured with the FLAME network. Further work is required, however, to fully automate the calculation of SO2 flux from the SO2 images captured with the camera, and to adequately account for scattering effects.
    Description: Published
    Description: 95-102
    Description: 3V. Dinamiche e scenari eruttivi
    Description: 5V. Sorveglianza vulcanica ed emergenze
    Description: JCR Journal
    Description: restricted
    Keywords: Stromboli ; SO2 flux ; VLP ; Explosion ; SO2 camera ; volcano monitoring ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Study on the Long-Period source mechanism at Campi Flegrei (Italy) (2012)
    Elsevier Science Limited
    Details
    Publication Date: 2020-12-15
    Description: The source properties of the Long-Period events that occurred at Campi Flegrei Caldera (Italy) during the 2004–2006 ground uplift episode are investigated by analyzing the temporal release of seismic energy, amplitude distribution and inter-event occurrence time. Moreover, an entropy-based decomposition method is applied to identify the simpler waveforms thought to be representative of the source mechanism of Long-Period events. On the basis of the outcomes, we propose that the main part of these events is the result of a source process triggered by a mechanism of fluid charge/discharge, which causes pressure drop in a main branch of a dentritic network of the hydrothermal system. In this model, the rate of the Poissonian process (about 15 min), which drives the occurrence of the Long-Period events, provides the average recharge time of the system up to the critical condition. A partial shunting of the fluid flow away from the main conduit activates the ”resonance” of a second branch, spatially separated from the first one. This is a process that occurs whenever the fluid pressure exceeds a critical value and produces less energetic Long-Period events. The mechanism of pressure variation in the two conduits generates signals with preferred amplitude scales, described by a bi-lognormal distribution. From a dynamical point of view, Long-Period events result well described by a low-dimensional dynamical system. Finally, the time pattern of the energy release and its correlation with the diurnal solid earth tide suggest that the whole mechanism of fluid charge/discharge is likely modulated by tidal stress variation.
    Description: Published
    Description: 16-30
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: partially_open
    Keywords: Lp sources ; Poissonian occurrence ; Tidal modulation ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    Slug Flow: Modeling in a Conduit and Associated Elastic Radiation (2012)
    Springer
    Details
    Publication Date: 2017-04-03
    Description: Among the eruptive styles, the Strombolian activity is one of the more easy to study because of its repetitive behavior. For this reason large amount of data can be comfortably collected. Strombolian volcanoes are like natural laborato- ries repeating the same experiment (individual explosions) many times each day. The development of quantitative models of eruptive dynamics is driven by the comparison of experimental ob- servations and synthetic data obtained through mathemat- ical, numerical or analogue modeling. Since Strombolian activity offers a profuse amount of interesting seismic signals, during the last decades there has been growing attention on seismological techniques aimed at retrieving the conduit geometry and the eruption dynamics from the seismological recordings. One of these techniques, the source function inversion, is able to re- trieve a summary of the forces acting on the volcanic con- duit during the VLP event generation [5]. The comparison of observed source functions with synthetic ones, obtained through numerical modeling, allow us to put constraints on the proposed models. Quantitative models, able to fit seismological observa- tions, are a powerful tool for interpreting seismic record- ings and therefor the seismological monitoring of active volcanoes.
    Description: Published
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: restricted
    Keywords: Strombolian activity ; Slug flow ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 10
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    Seismic insight into explosive paroxysms at Stromboli volcano, Italy (2012)
    Elsevier Science Limited
    Details
    Publication Date: 2017-04-04
    Description: At Stromboli volcano, Italy, continuous seismic monitoring and periodic, visual observations of volcanic activity for surveillance purposes began in the mid-1980s. Since 1985, two eruptions have occurred, one lasting from December, 1985 until April, 1986, and one in May, 1993. There have also been two small overflows, in 1990 and 1994. Since these episodes of lava effusion, the persistent Strombolian activity of the volcano has had several fluctuations during the past 15 years. Some episodes climaxed in powerful explosions. According to seismic records, these paroxysms consisted of a variable number of explosion quakes in rapid succession (i.e. from tens of seconds to a few minutes), associated with a notable increment in the amplitude of volcanic tremor. Throughout these episodes - which are called explosive sequences - lapilli, fragments of old rock, and bombs of varying dimensions were ejected, affecting an area greater than the crater terrace where the active craters are located. In this article, we describe the explosive sequences recorded at Stromboli between 1985 and 1999. We provide a characterization in terms of reduced displacement and duration for nine episodes occurring in 1998 and 1999. Their reduced displacements range from 15 to 124 cm2; their durations are between 6 and 18 min. We find no change in the frequency content of the seismic signal several minutes before and during the sequences. Considering medium- to long-term behavior, the spectral amplitude of the seismic signal decreases or has low values over several months preceding the occurrence of the paroxysms. This feature is common to 20 of the 22 explosive sequences, and is indicative of internal conditions that periodically characterize the feeder. We surmise that the paroxysms are the result of the partial obstruction of the volcanic conduit when the magma column is low or dropping. The onset of the explosive sequence, causing the sudden removal of the material which forms the obstruction, would trigger a sudden depressurization of the conduit and the rapid rise of magma from depth.
    Description: Published
    Description: 137-150
    Description: JCR Journal
    Description: reserved
    Keywords: Stromboli ; Paroxysms ; Seismicity ; Volcanoes ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 11
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    Seismic features of the June 1999 tectonic swarm in the Stromboli volcano region, Italy (2012)
    Elsevier Science Limited
    Details
    Publication Date: 2017-04-04
    Description: Crustal tectonic seismicity in the Southern Tyrrhenian Sea is characterized by the high occurrence rates of earthquakes to the west of the alignment of Salina, Lipari and Vulcano islands in the Aeolian archipelago. Only a few earthquakes affect the crustal region east of these islands, whereas intermediate and deep seismicity plays a relevant role. Based on this evidence, two aspects of the seismic swarm recorded at the Aeolian Island Seismic Network between June 6 and 17, 1999 looked anomalous. The first aspect concerned the number of earthquakes (78) that affected the Stromboli submarine edifice in a short time interval. Secondly, despite the low maximum magnitude Md 3.2 reached, the cumulative strain release was conspicuous in comparison with previous swarms in this region. We localized the swarm about 6 km northeast of Stromboli, at a depth between 8 and 12km. The source region was identified using standard methods of hypocentral location, as well as azimuth analysis. It is worth noting that the volcanic activity at Stromboli did not change significantly during the swarm nor throughout the following months. Therefore, the seismic swarm had no link with volcanic activity observed at the surface. Most of the earthquakes shared similar waveform and frequency content, and can be divided into families. We identified some earthquakes - with magnitude up to Md 3 - having relatively low frequency content at different seismic stations. This anomalous feature leads us to hypothesize the presence of fluid circulation and/or propagation of seismic waves in a ductile medium. Our hypothesis is in agreement with studies on marine geology, which highlight various forms of submarine volcanism in the southern basin of the Tyrrhenian Sea.
    Description: This work was financially supported by the EC project MULTIMO (Contract No. EVG1-CT-2000-00021).
    Description: Published
    Description: 121-136
    Description: JCR Journal
    Description: reserved
    Keywords: Earthquakes ; Seismic swarm ; Volcanoes ; Stromboli ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 12
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    Multiparametric Approach in Investigating Volcano-Hydrothermal Systems: the Case Study of Vulcano (Aeolian Islands, Italy) (2012)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: Seismic activity, ground deformation, and soil and fumarole temperatures acquired during 2004–2007 at Vulcano (Aeolian Islands) are analysed and the time relations among the different time series are discussed. Changes in temperature of fumarolic gases took place during four ‘‘anomalous’’ periods (November 2004–March 2005; October 2005–February 2006; August–October 2006; July–December 2007) at the same time as an increasing number of volcano-seismic events. In particular, the temperatures at high temperature vents and at steam heated soil ranged in time from 180 to 440 C and from 20 to 90 C, respectively. The maximum daily number of volcano-seismic events was 57, reached during the second anomalous period. This seismicity, characterised by focal depth generally lower than 1 km below sea level (b.s.l.) and composed of different kinds of events associated to both resonance and shear failure processes, is related to the shallow dynamics of the hydrothermal system. During the analysed period, very few volcano-tectonic earthquakes took place and tilt recordings showed no sharp or important changes. In light of such observations, the increases in both temperature and volcano-seismic events number were associated to increases in the release of gas from a deep and stable magma body, without magma intrusions within the shallow hydrothermal system. Indeed, a greater release of gas from depth leads to increased fluid circulation, that can promote increases in volcano-seismic events number by both fracturing processes and resonance and vibration in cracks and conduits. The different trends observed in the measured geochemical and geophysical series during the anomalous periods can be due to either time changes in the medium permeability or a changing speed of gas release from a deep magma body. Finally, all the observed variations, together with the changing temporal distribution of the different seismic event kinds, suggest that the hydrothermal system at Vulcano can be considered unsteady and dynamic.
    Description: Published
    Description: 167–182
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: reserved
    Keywords: Volcano seismolog ; soil and fumarole temperatures ; tilt data ; hydrothermal system ; Vulcano Island ; volcanic unrest ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
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  • 13
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    Seismological features of the Pernicana–Provenzana Fault System (Mt. Etna, Italy) and implications for the dynamics of northeastern flank of the volcano (2012)
    Elsevier Science Limited
    Details
    Publication Date: 2017-04-04
    Description: The Pernicana–Provenzana Fault System is one of the most active tectonic systems of Mt. Etna and it plays an important role in the dynamic of the eastern flank of the volcano. Earthquakes occurring close to this structural trend have reached magnitudes up to 4.2, sometimes with coseismic surface faulting, and have caused severe damages to tourist resorts and villages in the vicinity of this structure. In the last decade, a large number of shocks, sometimes in the form of swarms, linked to Pernicana–Provenzana Fault System movements have been detected by the permanent local seismic network operating in eastern Sicily. In this paper, we report on the detailed study of the seismic activity occurring during the 2000–2009 time span in the Pernicana–Provenzana Fault System area. Firstly, we located 407 earthquakes using a standard location code and a 1D crustal velocity model. We then applied two different approaches to calculate precise hypocenter locations of the events. In particular, a non-linear code was adopted to obtain an estimate of the a posteriori Probability Density Function in 3D space for the hypocenter location. Moreover, a relative location of correlated event pairs was performed, using the double-difference method. These two different location approaches allowed defining with good accuracy, the most active and hazarding sectors of the structure. The results of these precise locations showed a tighter clustering in the epicenters and in focal depths, in comparison with standard locations. Earthquakes are located along the Pernicana–Provenzana Fault System, and are mainly clustered in two zones, separated by an area with very low rate of earthquakes occurrence, but characterized by the highest energy release. Depths of the foci are very shallow, ranging between the surface and about 3 km b.s.l. Kinematics of the Pernicana–Provenzana Fault System, revealed by the fault plane solutions computed for the most energetic earthquakes, highlights a predominant dip–slip and left strike movements along E–W oriented fault planes, in agreement with field observations.
    Description: Published
    Description: 16-26
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Etna volcano ; Pernicana–Provenzana Fault System ; Earthquakes ; Precise location ; Fault plane solutions ; Seismic strain release ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 14
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    Acoustic Emission spectra classification from rock samples of Etna basalt in deformation-decompression laboratory experiments (2011)
    Springer
    Details
    Publication Date: 2020-02-24
    Description: Recent laboratory experiments on Etna basalt have permitted the generation of an extensive catalogue of acoustic emissions (AE) during two key experimental phases. Firstly, AE have been generated during triaxial compressional tests and formation of a complex fracture/damage zone. Secondly, rapid fluid decompression through the damage/shear zone after failure. We report new results from an advanced analysis method using AE spectrograms, allowing us to qualitatively identify high and low frequency events; essentially comparable to seismicity in volcanic areas. Our analysis, for the first time, quantitatively classifies ‘families’ of AE events belonging to the same experimental stage without prior knowledge. We then test the method using the AE catalogue for verification, which is not possible with field data. FFT spectra, obtained from AE, are subdivided into equal log intervals for which a local slope is calculated. Factor analysis has been then applied, in which we use a data matrix of columns representing the variables considered (frequency data averaged in bins) vs. rows indicating each AE data set. Factor analysis shows that the method is very effective and suitable for reducing data complexity, allowing distinct factors to be obtained. We conclude that most of the data variance (information content) can be well represented by three factors only, each one representing a well defined frequency range. Through the factor scores it is possible to represent data in a lower dimension factor space. Classification is then possible by identifying clusters of AE belonging to the same experimental stage. This allows us to propose a deformation/decompression interpretation based solely on the AE frequency analysis and to identify a third type of AE related to fluid movements in the deformation stage.
    Description: Published
    Description: 201-211
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: open
    Keywords: acoustic emissions ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.05. Volcanic rocks ; 05. General::05.01. Computational geophysics::05.01.04. Statistical analysis
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 15
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    Source location of long period seismicity at Volcàn de Colima, México (2011)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: This paper presents an analysis of seismicity associated with the volcanic activity of Volcàn de Colima (México) and recorded in the period November 2005–April 2006 during a field survey by the Istituto Nazionale di Geofisica e Vulcanologia (INGV)–Osservatorio Vesuviano, the Observatorio Vulcanologico de Colima of Colima University and the Instituto Andaluz de Geofisica, University of Granada. Three different types of volcanic earthquakes have been identified on the basis of their spectral properties: Type A (0.3–1 Hz), Type B (1–5 Hz) and Type C (3–4 Hz). Results of polarization analysis applied to Type A events show a predominance of radial motion, indicating that the wavefield comprises compressional waves (P) and shear waves polarized in the vertical plane (SV), while the signal always begins with a negative polarity. Type A, B and C earthquakes have been located using both a flat layered model and a 3D model including topography. Hypocentre distributions indicate that the source of Type A signals is very shallow and confined to a small volume lying about 1 km below the crater. In contrast, the source of Type B and C events is significantly deeper, with most hypocentres located in a volume of about 1 km3 centred at 2.5–3 km depth. A cluster analysis based on the crosscorrelation among the waveforms of different events recorded at the same station was applied to Type A earthquakes. Only two clusters, which include only a small percentage of events were found, indicating that earthquake families were uncommon during the period of our survey.
    Description: Published
    Description: 887-898
    Description: 3.1. Fisica dei terremoti
    Description: JCR Journal
    Description: reserved
    Keywords: Colima Volcano ; Long Period Events ; Earthquake location ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 16
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    Towards an automatic monitoring system of infrasonic events at Mt. Etna: strategies for source location and modelling (2010)
    Springer
    Details
    Publication Date: 2020-11-16
    Description: Active volcanoes characterized by open conduit conditions generate sonic and infrasonic signals, whose investigation provides useful information for both monitoring purposes and studying the dynamics of explosive processes. In this work, we discuss the automatic procedures implemented for a real-time application to the data acquired by a permanent network of five infrasound stations running at Mt. Etna volcano. The infrasound signals at Mt. Etna consist in amplitude transients, called infrasound events. The adopted procedure uses a multi-algorithm approach for event detection, counting, characterization and location. It is designed for an efficient and accurate processing of infrasound records provided by single-site and array stations. Moreover, the source mechanism of these events can be investigated off-line or in near real-time by using three different models: i) Strombolian bubble; ii) resonating conduit and iii) Helmholtz resonator. The infrasound waveforms allow us to choose the most suitable model, to get quantitative information about the source and to follow the time evolution of the source parameters.
    Description: Published
    Description: 1215–1231
    Description: 6V. Pericolosità vulcanica e contributi alla stima del rischio
    Description: JCR Journal
    Description: open
    Keywords: infrasound ; monitoring system ; Mt. Etna ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 17
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    Towards an Automatic Monitoring System of Infrasonic Events at Mt. Etna: Strategies for Source Location and Modeling (2010)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: Active volcanoes characterized by open conduit conditions generate sonic and infrasonic signals, whose investigation provides useful information for both monitoring purposes and studying the dynamics of explosive processes. In this work, we discuss the automatic procedures implemented for a real-time application to the data acquired by a permanent network of five infrasound stations running at Mt. Etna volcano. The infrasound signals at Mt. Etna consist in amplitude transients, called infrasound events. The adopted procedure uses a multi-algorithm approach for event detection, counting, characterization and location. It is designed for an efficient and accurate processing of infrasound records provided by single-site and array stations. Moreover, the source mechanism of these events can be investigated off-line or in near real-time by using three different models: (1) Strombolian bubble; (2) resonating conduit and (3) Helmholtz resonator. The infrasound waveforms allow us to choose the most suitable model, to get quantitative information about the source and to follow the time evolution of the source parameters.
    Description: Published
    Description: 1215–1231
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Infrasound ; monitoring system ; Mt. Etna volcano ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.07. Instruments and techniques
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 18
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    Time-space variation of volcano-seismic events at La Fossa (Vulcano, Aeolian Islands, Italy): new insights into seismic sources in a hydrothermal system (2010)
    Springer
    Details
    Publication Date: 2020-02-24
    Description: We investigated the relationship between volcano-seismic events, recorded at La Fossa crater of Vulcano (Aeolian Islands, Italy) during 2004-2006, and the dynamics of the hydrothermal system. During the period of study, three episodes of increasing numbers of volcano-seismic events took place at the same time as geothermal and geochemical anomalies were observed. These geothermal and geochemical anomalies have been interpreted as resulting from an increasing deep magmatic component of the hydrothermal fluids. Three classes of seismic events (long period, high frequency and monochromatic events), characterised by different spectral content and various similarity of the waveforms, have been recognised. These events, clustered mainly below La Fossa crater area at depths of 0.5–1.1 km b.s.l., were space-distributed according to the classes. Based on their features, we can infer that such events at Vulcano are related to two different source mechanisms: (1) fracturing processes of rocks and (2) resonance of cracks (or conduits) filled with hydrothermal fluid. In the light of these source mechanisms, the increase in the number of events, at the same time as geochemical and geothermal anomalies were observed, was interpreted as the result of an increasing magmatic component of the hydrothermal fluids, implying an increase of their flux. Indeed, such variation caused an increase of both the pore pressure within the rocks of the volcanic system and the amount of ascending fluids. Increased pore pressures gave rise to fracturing processes, while the increased fluid flux favoured resonance and vibration processes in cracks and conduits. Finally, a gradual temporal variation of the waveform of the hybrid events (one of the subclasses of long period events) was observed, likely caused by heating and drying of the hydrothermal system.
    Description: Published
    Description: 803-816
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Volcano seismology ; Vulcano Island ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 19
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    Volcanological inferences from seismic-strain tensor computations at Mt. Etna Volcano, Sicily (2008)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: Kostrov's (1974) algorithm for seismic-strain tensor computations, in the version implemented by Wyss et al. (1992a) for error estimates, has been applied to shear-type earthquakes occurring beneath the Etna volcano during 1990-1996. Space-time variations of strain orientations and amplitudes have been examined jointly with ground-deformation and gravimetric data collected in the same period and reported in the literature. Taking also into account the information available from volcanological observations and structural geology, we propose a model assuming that hydraulic pressure by magma emplaced in nearly north-south vertical structures produces the E-W orientation of the maximum compressive strain found in the upper 10 km beneath the crater area. In contrast, regional tectonics deriving from the slow, north-south convergence between the African and European plates appear to play a dominant role in the generation of stress and strain fields at crustal depths deeper than 10 km below the volcano. According to our interpretation, the progressive ascent of magma through the upper crust prior to eruption produces the observed gravity changes, cone inflation and unusual seismic strain rate in the upper 10 km associated with a more sharply defined seismic deformation regime (i.e. very small confidence limits of the epsilon 1 orientation). In agreement with this model, deflation revealed by ground-deformation data during the course of the major 1991-1993 eruption was accompanied by a practically nil level of shallow seismicity.
    Description: Published
    Description: 318-330
    Description: JCR Journal
    Description: open
    Keywords: Mt. Etna ; Italy ; Earthquakes ; Seismic strain ; Stress inversion ; Volcanic processes ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 20
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    Seismic Coda Q and Turbidity Coefficient at the Phlegraean Fields Volcanic Area: Preliminary Results (2007)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: In the text
    Description: Published
    Description: 219-224
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: open
    Keywords: coda Q ; Phlegraean Fielsa ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 21
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    High precision locations of LP events on Mt. Etna: reconstruction of the fluid-filled volume (2007)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: During 1991−93 at Mount Etna, long-period (LP) events occurring in swarms characterized the evolution of the eruption. The presence of multiplets i.e. groups of events with similar waveform signatures, has been recognized within this activity. Traditional techniques for locating LP events do not allow obtaining reliable hypocenters, which have only succeeded in placing earthquakes in a roughly 1 km2 area slightly east of the Mt. Etna Northeast Crater. Hypocenters have been relocated in two steps: the absolute location has been improved using Thurber’s code and a complex 3D velocity model; a highly precise relative location has been applied on multiplets to define the source geometry. 3D locations and high precision analysis suggest that during the 1991−93 eruption the resonator producing LP events was a part of the uppermost Northeast Crater conduit, measuring 210 meters in height and 45−50 meters in diameter.
    Description: Published
    Description: 663-674
    Description: reserved
    Keywords: waveform correlation ; stacked events ; 1991−93 eruption ; conduct geometry ; Mt. Etna Northeast Crater ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 22
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    Intrusive Mechanisms at Mt. Etna Forerunning the July-August 2001 Eruption from Seismic and Ground Deformation Data (2005)
    Springer
    Details
    Publication Date: 2017-04-04
    Description: In this work we present seismological and ground deformation evidence for the phase preparing the July 18 to August 9, 2001 flank eruption at Etna. The analysis performed, through data from the permanent seismic and ground deformation networks, highlighted a strong relationship between seismic strain release at depth and surface deformation. This joint analysis provided strong constraints on the magma rising mechanisms. We show that in the last ten years, after the 1991–1993 eruption, an overall accumulation of tension has affected the volcano. Then we investigate the months preceding the 2001 eruption. In particular, we analyse the strong seismic swarm on April 20–24, 2001, comprising more than 200 events (Mmax = 3.6) with prevalent dextral shear fault mechanisms in the western flank. The swarm showed a ca. NE-SW earthquake alignment which, in agreement with previous cases, can be interpreted as the response of the medium to an intrusive process along the approximately NNW-SSE volcano-genetic trend. These mechanisms, leading to the July 18 to August 9, 2001 flank eruption, are analogous to ones observed some months before the 1991–1993 flank eruption and, more recently, in January 1998 before the February-November 1999 summit eruption.
    Description: Published
    Description: 1469-1487
    Description: partially_open
    Keywords: Ground deformation ; volcano seismology ; Mt. Etna Volcano ; intrusive mechanism ; 04. Solid Earth::04.03. Geodesy::04.03.01. Crustal deformations ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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