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  • Articles  (19)
  • 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry  (11)
  • 04. Solid Earth::04.04. Geology::04.04.09. Structural geology  (8)
  • AGU  (13)
  • Blackwell Publishing Ltd  (5)
  • Nature Publishing Group
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  • Articles  (19)
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  • 1
    Publication Date: 2020-11-12
    Description: Accepted for publication in Journal of Geophysical Research. Copyright (2010) American Geophysical Union.
    Description: Carbon dioxide (CO2) diffuse degassing structures (DDS) at Furnas Volcano (São Miguel Island, Azores) are mostly associated with the main fumarolic fields, evidence that CO2 soil degassing is the surface expression of rising steam from the hydrothermal system. Locations with anomalous CO2 flux are mainly controlled by tectonic structures oriented WNW-ESE and NW-SE and by the geomorphology of the volcano, as evidenced by several DDS located in depressed areas associated with crater margins. Hydrothermal soil CO2 emissions in Furnas volcano are estimated to be ~ 968 t d-1. Discrimination between biogenic and hydrothermal CO2 was determined using a 1 statistical approach and the carbon isotope composition of the CO2 efflux. Different sampling densities were used to evaluate uncertainty in the estimation of the total CO2 flux, and showed that a low density of points may not be adequate to quantify soil emanations from a relatively small DDS. Thermal energy release associated to diffuse degassing at Furnas caldera is about 118 MW (from an area of ~ 4.8 km2) based on the H2O/CO2 ratio in fumarolic gas. The DDS affect also Furnas and Ribeira Quente villages, which are located inside the caldera and in the south flank of the volcano, respectively. At these sites, 58% and 98% of the houses are built over hydrothermal CO2 emanations, and the populations are at risk due to potential high concentrations of CO2 accumulating inside the dwellings. Keywords: Soil diffuse degassing; soil CO2 flux; emission rates; Azores archipelago 2
    Description: Published
    Description: B12208
    Description: 3V. Proprietà chimico-fisiche dei magmi e dei prodotti vulcanici
    Description: JCR Journal
    Description: open
    Keywords: Soil CO2 emissions ; Furnas volcano ; volcano monitoring. ; 04. Solid Earth::04.04. Geology::04.04.11. Instruments and techniques ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
    Publication Date: 2017-04-04
    Description: Radon emissions are frequently monitored in volcanically and tectonically active areas in order to reveal changes in soil degassing, as radon acts a tracer for the more abundant CO2 degassing commonly observed in such areas. Between July 2002 and May 2003 a series of discrete measurements of radon concentrations in soil were made with high spatial resolution (∼5–100 m) in the Santa Venerina area on Mt. Etna. These measurements revealed well-defined linear anomalies that we interpret as being caused by active faults whose higher porosity than surrounding soils allows an increased CO2 flux, carrying radon from beneath. These faults were not visible at the surface and were therefore revealed at high spatial resolution by our radon survey. Our hypothesis that the positive anomalies are attributable to active faults was strengthened by the observation of concentrated damage along this geometry during the earthquakes that struck this area in late October 2003.
    Description: Published
    Description: 4
    Description: partially_open
    Keywords: Structural Geology: Role of fluids ; Structural Geology: Fractures and faults ; Structural Geology: Instruments and techniques ; Volcanology: Instruments and techniques ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
    Publication Date: 2017-04-04
    Description: This study concerns the unstable scarp named Sciara del Fuoco (SDF) at Stromboli volcano, merging geostructural observations, live-cam records in the visible and IR bands, analysis of vertical aerial photographs, and seismic records. These are used to assess morpho-structural changes between 2002 and 2004. The onset of the lava effusion on 28 December, 2002 preceded a gravitational collapse by two days, affecting a wide area of the SDF above and below sea level. We surmise that the collapse enhanced latent instability of the scarp. The 2002–2003 lava flows had a remarkable stabilizing effect on wide portions (〉50%) of the SDF, whilst erosive phenomena continued in the zone not covered by lava. This caused unrelenting regression of the upper landslide scarp toward the summit craters in the form of rockfalls and debris flows. If the crater conduit were involved in the sliding, then a change in eruptive behavior cannot be excluded.
    Description: Published
    Description: L09304
    Description: reserved
    Keywords: NONE ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 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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  • 4
    Publication Date: 2017-04-04
    Description: More than 100 3 ~ e / 4i~soeto pe ratios were measured in CO,-dominated gas samples collected during the 1997-1 998 seismic crisis that shook the Umbria-Marche, Central Apennines, Italy. Although the gas emissions were located in a typical "crustal" environment the measured values delineate variable mixing proportions between mantle-derived and crustal helium. During the monitoring period anomalous 3 ~ e P r~atieos were observed, together with a significant increase of fluid outflows. The observed 3 ~ e Pa~noema lies appear to be driven by stress-induced crustal deformations affecting micro-fracturing and bulk permeability and, in turn, by a seismogenic-induced modification of the crustal permeability of rocks. Since crustal deformations can also occur aseismically, the geochemical anomalies must be considered indicators of processes occurring below the surface, which could eventually help to estimate the probability increase of an impending earthquake, instead of pure empirical precursors.
    Description: Published
    Description: 839-842
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: helium ; earthquakes ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
    Publication Date: 2017-04-04
    Description: Soil radon emissions have been proved as a useful tool for predicting earthquakes and volcanic eruptions and furthermore aided in determining the location of active faults. Continuous radon monitoring was carried out near Southeast Crater of Mt. Etna in September–November 1998, during a period of frequent eruptive episodes at that crater. Radon anomalies were detected when eruptive episodes and the accompanying volcanic tremor became increasingly intense: no anomalies in radon activity were observed during the first five, and weaker, eruptive episodes, whereas significant spikes in radon activity preceded the latter five episodes by ≥46 hours. This probably reflects increased gas leakage through fractures intersecting the shallow plumbing system, as gas pressure in the Southeast Crater conduit became higher with time. Radon monitoring thus might serve to better understand eruptive mechanisms and possible precursors, making further studies in this field a promising perspective.
    Description: Published
    Description: 1-4
    Description: partially_open
    Keywords: Seismology: Volcano seismology ; Structural Geology: Role of fluids ; Volcanology: Volcano monitoring ; Volcanology: Instruments and techniques ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 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)
    Type: article
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  • 6
    Publication Date: 2017-04-04
    Description: Geodynamic evolution of southern Italy can be understood within the framework of the Mediterranean- Alpine System. Subduction of a plate along the Sicily- Calabrian forearc under the Tyrrhenian Sea has been suggested by many geophysicists, although it is not yet confirmed and remains somewhat controversial. Helium isotope ratios provide useful information on the geotectonic structure of the region. We report here the 3He/4He ratios of terrestrial gas samples from southern Italy. The observed 3He/4He ratios are relatively high in the Eolian volcanic arc region and low in the other areas. Dichotomous explanations are presented. Firstly volcanic arc-forearc hypothesis suggests the subduction along the Sicily-Calabrian forearc. Secondly horizontal transport hypothesis is described based on the relationship between the ratios and radial distance from the recent spreading basin in Southern Tyrrhenian Sea.
    Description: Published
    Description: 511-514
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: open
    Keywords: helium isotopes ; tectonics ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
    Publication Date: 2017-04-04
    Description: Dikes provide crucial information on how magma propagates within volcanoes. Somma-Vesuvio (Italy) consists of the active Vesuvio cone, partly bordered by the older Mt. Somma edifice. Historical chronicles on the fissure eruptions in 1694–1944 are matched with an analytical solution to define the propagation path of the related dikes and to study any control of the Mt. Somma relief. The fissures always consisted of the downslope migration of vents from an open summit conduit, indicating lateral propagation as the predominant mechanism for shallow dike emplacement. No fissure emplaced beyond Mt. Somma, suggesting that its buttressing hinders the propagation of the radial dikes. An analytical solution is defined to describe the mechanism of formation of the laterally propagating dikes and to evaluate the effect of topography. The application to Somma-Vesuvio suggests that, under ordinary excess magmatic pressures, the dikes should not propagate laterally at depths 〉240–480 m below the surface, as the increased lithostatic pressure requires magmatic pressures higher than average. This implies that, when the conduit is open, the lateral emplacement of dikes is expectable on the S, Wand E slopes. The lack of fissures N of Mt. Somma is explained by its buttressing, which hinders dike propagation. Citation: Acocella, V., M. Porreca, M. Neri, E. Massimi, and M. Mattei (2006), Propagation of dikes at Vesuvio (Italy) and the effect of Mt. Somma, Geophys. Res. Lett., 33, L08301, doi:10.1029/2005GL025590.
    Description: Published
    Description: L08301
    Description: reserved
    Keywords: NONE ; 01. Atmosphere::01.01. Atmosphere::01.01.03. Pollution ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 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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  • 8
    Publication Date: 2017-04-04
    Description: Understanding how shallow magma is emplaced within volcanoes is crucial for hazard assessment. The 2002–2003 Stromboli eruption provides the opportunity to investigate shallow magma emplacement resulting from orthogonal feeder dikes and its possible effects. Stromboli erupted in 2002–2003, when effusive activity replaced Strombolian activity. On December 28, a NE-SW fissure propagated from the lava-filled northernmost summit crater. On December 29, a NW-SE fissure propagated north of the craters, feeding NW-SE aligned vents. On December 30, this area collapsed, reaching the sea and generating a tsunami. In mid February 2003, the NW-SE fissure became inactive, while the NE-SW effusive fissure continued until July. A model for shallow magma emplacement is proposed. The lateral propagation of a NE-SW dike from the northernmost crater was triggered. Below, a NW-SE dike, propagating from the magma-filled NE tip of the NE-SW elongated conduit, fed the NW-SE aligned vents. In February, the conduit periphery became solidified, freezing the NW-SE dike, and the transport of magma was limited to the central part, focusing its rise below the craters. This fed the NE-SW fissure until the supply decreased further (July), returning to the ordinary level sustaining Strombolian activity. Orthogonal dike emplacement followed the trajectories of the maximum (gravitational) stress s1, partly controlled by the irregular topography of the uppermost edifice. The emplacement of orthogonal dikes in a limited area is feasible at non-perfectly conical active volcanoes, where the maximum gravitational stress may show variations from a purely radial path.
    Description: Published
    Description: L17310
    Description: reserved
    Keywords: NONE ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
    Publication Date: 2017-04-04
    Description: This paper presents the results of hydrogeochemical and seismological studies carried out at Mt. Vesuvius during the period June 1998 – December 2005. Hydrogeochemical data show the occurrence of slowly varying long-term variations in the total dissolved salts and bicarbonate contents of the groundwaters, accompanied by a general decline in water temperatures. The temporal distributions of air temperature and rainfall in the Vesuvius area suggest that these variations do not depend on changes in the hydrological regime. The changes in the geochemical parameters are accompanied by slight variations in both the seismicity rate and energy release. A further relationship between seismic activity and fluid discharge rate is highlighted by a particular episode that occurred in August 2005, when a soil thermal anomaly was observed a few weeks before the occurrence of a very shallow earthquake. Moment-tensor analysis of this earthquake suggests that the most plausible source mechanism is a shear faulting combined with the opening of tensile crack. This feature is often observed in volcanic areas and it is usually related to fluid-/gas-driven rock fracturing. The observed seismological, hydrological, and geochemical temporal changes are interpreted not as changes of the volcanic system, but in terms of an external forcing as identified in the variation of the regional and local stress field acting on the volcano. This study has inferences onto the evaluation of the state of activity of volcanic systems and the eventual detection of unrest phenomena.
    Description: Published
    Description: B05206
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Vesuvius ; seismicity ; fluid circulation ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
    Publication Date: 2017-04-04
    Description: We report measurements of Hg, SO2, and halogens (HCl, HBr, HI) in volcanic gases from Masaya volcano, Nicaragua, and gaseous SO2 and halogens from Telica volcano, Nicaragua. Mercury measurements were made with a Lumex 915+ portable mercury vapor analyzer and gold traps, while halogens, CO2 and S species were monitored with a portable multi gas sensor and filter packs. Lumex Hg concentrations in the plume were consistently above background and ranged up to 350 ng/m3. Hg/SO2 mass ratios measured with the real-time instruments ranged from 1.1*10-7 to 3.5*10-5 (mean 2*10-5). Total gaseous mercury TGM)concentrations measured by gold trap ranged from 100 to 225 ng/m3. Reactive gaseous mercury accounted for 1% of TGM, while particulate mercury was 5% of the TGM. Field measurements of Masaya’s SO2 flux, combined with the Hg/SO2 ratio, indicate a Hg flux from Masaya of 7.2 Mg/a-1. At Masaya’s low temperature fumaroles, Hg/CO2 mass ratios were consistently around 2*10-8, lower than observed in the main vent (Hg/CO2 10-7). Low-temperature fumarole Hg fluxes from Masaya are insignificant (150 g a-1). Ratios of S, C and halogen species were also measured at Masaya and Telica volcanoes. CO2/SO2 ratios at Masaya ranged from 2.8 to 3.9, comparable to previously published values. At Masaya molar Br/SO2 was 3*10-4 and I/SO2 was 2*10-5, suggesting fluxes of 0.2–0.5 Mg HBr d-1 and 0.02–0.05 Mg HI d-1. At Telica the Br/SO2 ratio was also 3*10-4 and the I/SO2 ratio was 5.8*10-5, with corresponding fluxes of 0.2 Mg HBr d-1 and 0.06 Mg HI d-1. Gases at both volcanoes are enriched in I relative to Br and Cl, compared to gases from volcanoes elsewhere.
    Description: This work was funded by NERC grant NE/ C511180/1/.
    Description: Published
    Description: B06203
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: reserved
    Keywords: Mercury ; Halogen ; Volcanic emissions ; Masaya volcano ; Telica volcano ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 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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