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  • 1
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    Denoising gravity and geomagnetic signals from Etna volcano (Italy) (2008)
    Copernicus Publications
    Details
    Publication Date: 2017-04-04
    Description: Multivariate methods were applied to denoise the gravity and geomagnetic signals continuously recorded by the permanent monitoring networks on the Etna volcano. Gravity and geomagnetic signals observed in volcanic areas are severely influenced by meteorological variables (i.e. pressure, temperature and humidity), whose disturbances can make the detection of volcanic source effects more difficult. For volcano monitoring it is necessary, therefore, to reduce the effects of these perturbations. To date filtering noise is a very complex problem since the spectrum of each noise component has wide intervals of superposition and, some times, traditional filtering techniques provide unsatisfactory results. We propose the application of two different approaches, the adaptive neuro-fuzzy inference system (ANFIS) and the Independent Component Analysis (ICA) to remove noise effects from gravity and geomagnetic time series. Results suggest a good efficiency of the two proposed approaches since they are capable of finding and effectively representing the underlying factors or sources, and allow local features of the signal to be detected.
    Description: Published
    Description: 735-749
    Description: 2.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attive
    Description: JCR Journal
    Description: open
    Keywords: gravity data ; geomagnetic data ; ANFIS ; ICA ; Etna volcano ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Volcanomagnetic changes accompanying the onset of the 2002–2003 eruption of Mt. Etna (Italy) (2005)
    Elsevier
    Details
    Publication Date: 2017-04-03
    Description: Remarkable changes in the local magnetic field were associated with the onset of the 2002–2003 flank eruption at Mt. Etna. After differential magnetic field measurements were filtered from the external noise by using adaptive filters, we recognized two stages in the total intensity changes, which are closely related to different volcanic events: (a) rapid variations of about 4–5 nT associated with October 26 seismic swarm recorded beneath the summit craters; (b) step-like variations of 9–10 nT coincident with October 27 eruptive fissures opening up in the north flank. These observations are generally consistent with those calculated from simple magnetic models of these volcanic processes, in which the magnetic changes are generated by stress redistribution due to magmatic intrusions at different depth. The magnetic data not only allow the timing of the intrusive event to be described in greater detail but also, together with other volcanological and geophysical evidences, permit some constraints to be set on the characteristics of propagation of a shallow dike. Firstly, at around midnight on 26 October magma was rapidly injected to a depth of 3–4 km just below the summit craters. Secondly, after 1:00 on 27 October, continued intrusion magma occurred upward and culminated a few hundred meters below the free surface fractured along a N–E direction. Thirdly, at about 2:28, magma gave rise to an explosive fissural vent at the northern base of the NE crater near 3000 m a.s.l. Finally, at about 5:00, the first eruptive fissure became active along the eastern border of the NE rift at 2500 m a.s.l. The rate of growth of the magnetic anomalies, moreover, leads to the interpretation that the magmatic intrusion travelled northward from base of the NE crater to the NE rift at approximately 14 m/min.
    Description: Published
    Description: 1-14
    Description: partially_open
    Keywords: eruptions ; monitoring ; magnetic methods ; volcanomagnetic modeling ; Mt. Etna ; 04. Solid Earth::04.05. Geomagnetism::04.05.04. Magnetic anomalies ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 520 bytes
    Format: 1461844 bytes
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    Format: application/pdf
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  • 3
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    Numerical simulation of stress induced piezomagnetic fields at Etna volcano (2009)
    Blackwell Publishing
    Details
    Publication Date: 2017-04-04
    Description: 3-D magneto-elastic models based on finite element method (FEM) have been developed to compute piezomagnetic fields caused by magmatic overpressure sources.We solved separately (i) the elastostatic equation for the stress field and (ii) the coupled Poisson’s equation for magnetic potential field. The numerical computationswere focused on a more realistic modelling of Etna volcano, where remarkable magnetic changes have been observed during eruptive events. We evaluated the effects of topography and medium heterogeneities considering different multilayered crustal structures constrained by seismic tomography and geological evidences. When topography and magneto-elastic heterogeneities are included in the numerical models,the piezomagnetic field changes show significant deviations from the homogeneous half-space solution. Generally, it was found that the analytical model overestimates the expected magnetic changes. The numerical models of the piezomagnetic field showed significant differences in presence of strong magnetization contrasts and in proximity of steep cliffs, that is, at the volcano summit. The FEM approach presented here allows considering a picture of a fully 3-D model of Etna volcano, which could advance the reliability of model-based assessments of magnetic observations.
    Description: Published
    Description: 1469-1476
    Description: 2.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attive
    Description: JCR Journal
    Description: reserved
    Keywords: Numerical solutions ; Magnetic anomalies: modeling and interpretation ; Volcano monitoring ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    Variazioni di gravità osservate all’Etna nel 1994 lungo il profilo Adrano-Sapienza-Zafferana (2015)
    Details
    Publication Date: 2015-08-17
    Description: INGV
    Description: Published
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: open
    Keywords: gravity ; Etna ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: report
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  • 5
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    Volcanomagnetic Evidence of the Magmatic Intrusion on 13th May 2008 (2008)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: During the onset of 2008 volcanic crisis at Mt Etna, the near-real time magnetic data provided a continuous updating of the volcano activity state on the northern flank. On the morning of 13th May 2008, significant local magnetic field changes marked the resumption of the eruptive activity characterized by the opening of a fracture field on the northern flank, and an eruptive fissure in the Valle del Bove. In agreement with the northward propagation of seismic events, magnetic signals at 5 stations in the summit area revealed a nearly NNW-SSE oriented magmatic intrusion, which started at about 9:00 GMT, propagated northward for about 2 km, and stopped at 14:00 GMT before reaching the North-East Rift. Magnetic variations, with amplitude ranging between 1.8 nT and -6.5 nT, are consistent with those calculated from piezomagnetic models, where stress-induced changes in rock magnetization are produced by the magmatic intrusion.
    Description: Published
    Description: L22301
    Description: 2.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attive
    Description: JCR Journal
    Description: partially_open
    Keywords: Mt Etna ; volcano monitoring ; piezomagnetic field ; magmatic intrusion ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
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    3D integrated geophysical modeling for the 2008 magma intrusion at Etna: Constraints on rheology and dike overpressure (2012)
    Details
    Publication Date: 2017-04-04
    Description: We present a 3D numerical model based on Finite Element Method (FEM) to jointly evaluate geophysical changes caused by dislocation and overpressure sources in volcanic areas. A coupled numerical problem was solved to estimate ground deformation, gravity and magnetic changes produced by stress redistribution accompanying magma migration within the volcano edifice. We successfully applied the integrated numerical procedure to image the magmatic intrusion occurring in the northern flank of Etna during the onset of the 2008 eruption. A multi-layered crustal structure of the volcano constrained by geological models and geophysical data was considered. Geodetic and gravity data provide information on the strain field, while piezomagnetic changes give constraints on the stress field. Therefore, the integrated modeling gives insights on Mt Etna rheology and dike overpressure involved in the magma propagation and improves understanding of dike emplacement in the northern sector of the volcano. Our FEM-based approach improves the reliability of model-based inference of geophysical parameters obtained during monitoring of the onset of Etna lateral intrusions that can prelude to an impending eruption.
    Description: Published
    Description: 44-52
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: Mt Etna ; magmatic intrusion ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 7
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    Combining relative and absolute gravity measurements to enhance volcano monitoring (2013)
    Springer Berlin Heidelberg
    Details
    Publication Date: 2017-04-04
    Description: To achieve a balance between uncertainty and efficiency in gravity measurements, we have investigated the applicability of combined measurements of absolute and relative gravity as a hybrid method for volcano monitoring. Between 2007 and 2009, three hybrid gravity surveys were conducted at Mt Etna volcano, in June 2007, July 2008, and July 2009. Absolute gravity data were collected with two absolute gravimeters, which represent the state of the art in recent advances in ballistic gravimeter technology: (1) the commercial instrument FG5#238 and (2) the prototype instrument IMGC-02. We carried out several field surveys and confirmed that both the absolute gravimeters can still achieve a 10 μGal or better uncertainty even when they are operated in severe environmental conditions. The use of absolute gravimeters in a field survey of the summit area of Mt Etna is unprecedented. The annual changes of the gravity measured over 2007–2008 and 2008–2009 provide unequivocal evidence that during the 2007–2009 period, two main phenomena of subsurface mass redistribution occurred in distinct sectors of the volcano, accompanying different eruptive episodes. From 2007 to 2008, a gravity change of −60 μGal was concentrated around the North- East Rift. This coincided with a zone affected by strong extensional tectonics, and hence might have been related to the opening of new voids. Between 2008 and 2009, a North-South elongate feature with a maximum gravity change of +80 μGal was identified in the summit craters area. This is interpreted to indicate recharge of a deepintermediate magma storage zone, which could have occurred when the 2008–2009 eruption was still ongoing.
    Description: Published
    Description: 1745-1756
    Description: 2.6. TTC - Laboratorio di gravimetria, magnetismo ed elettromagnetismo in aree attive
    Description: JCR Journal
    Description: restricted
    Keywords: Mt Etna . Relative gravity . Absolute gravity . ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 8
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    Toward a realistic deformation model of the 2008 magmatic intrusion at Etna from combined DInSAR and GPS observations (2012)
    Details
    Publication Date: 2020-02-24
    Description: The combination of (i) DInSAR data, capable of observing deformation pattern at a spatial resolution unachievable with other sparse geodetic measurements, (ii) continuous GPS data, able to provide temporal constraints on source evolution, and (iii) numerical modeling procedures, appropriate to consider a non-uniform opening distribution of a source embedded in a 3D heterogeneous medium, allowed us to infer a complex and realistic deformation model of the magmatic intrusion that occurred in the northern flank of Etna on 13 May 2008. Numerical modeling of ground deformation data defines a near-vertical dyke intruded for 2.5 km starting from a depth of 1400 m asl right below the summit craters and reaching shallow crust level in the northern flank. From the estimated opening distribution of the propagating magma-filled crack, which reached a maximum value of about 2 m, a volumetric expansion of crustal rocks of about 5.3 x 10^6 m^3 was obtained. Also, we clarified the temporal evolution of the northward magmatic intrusion, which lasted just over 5 hours with an initial magma propagation velocity of about 1.2 km/h, and decreased to about 0.24 km/h as the driving pressure lowered due to the effusive activity started at southern vents.
    Description: Published
    Description: 22-27
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: Magmatic Intrusion ; Numerical simulation ; DInSAR data ; GPS data ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 9
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    From source to surface: dynamics of Etna’s lava fountains investigated by continuous strain, magnetic, ground and satellite thermal data (2013)
    Springer Berlin Heidelberg
    Details
    Publication Date: 2020-02-24
    Description: We investigated the eruptive episodes that occurred at Etna volcano on 15 November 2011 and 18 March 2012 using different types of data. We present novel data from two recently installed strainmeters that recorded unique signals during the lava fountain phases of these events. The strainmeter data, integrated with those recorded by the magnetic network, and with satellite and ground thermal data, allowed us to follow the path of a gas-rich magma batch from the source inside the volcano to the surface and atmosphere. The amplitude ratio of the volumetric strain changes constrained the storage depth of the magma feeding the lava fountains above 1.5 km below sea level. Magnetic data revealed an attempted shallow lateral intrusion, whereas ground and satellite thermal data furnished a quantification of the total erupted volumes of ∼2.2×106m3 for the 15 November event and ∼3.0×106m3 for the 18 March event. Despite different durations of the explosive and effusive phases of the two lava fountain events, the total erupted volume was quite similar, suggesting the emptying of a shallow storage system displaying a steady behaviour.
    Description: Published
    Description: article 690
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: restricted
    Keywords: Etna volcano ; lava fountain ; strain ; magnetic data ; thermal data ; 04. Solid Earth::04.08. Volcanology::04.08.06. Volcano monitoring
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 10
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    First observations of the fumarolic gas output from a restless caldera: implications for the current period of unrest (2005-2013) at Campi Flegrei (2015)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: The fumarolic gas output has not been quantified for any of the currently deforming calderas worldwide, due to the lack of suitable gas flux sensing techniques. In view of resumption of ground uplift (since 2005) and the associated variations in gas chemistry, Campi Flegrei, in southern Italy, is one of the restless calderas where gas flux observations are especially necessary. Here we report the first ever obtained estimate of the Campi Flegrei fumarolic gas output, based on a set of MultiGAS surveys (performed in 2012 and 2013) with an ad-hoc-designed measurement setup. We estimate that the current Campi Flegrei fumarolic sulphur (S) flux is low, on the order of 1.5–2.2 tons/day, suggesting substantial scrubbing of magmatic S by the hydrothermal system. However, the fumarolic carbon dioxide (CO2) output is ∼460±160 tons/day (mean±SD), which is surprisingly high for a dormant volcano in the hydrothermal stage of activity, and results in a combined (fumaroles + soil) CO2 output of ∼1560 tons/day. Assuming magma to be the predominant source, we propose that the current CO2 output can be supplied by either (i) a large (0.6–4.6 km3), deeply stored (〉7 km) magmatic source with low CO2 contents (0.05–0.1 wt%) or (ii) by a small to medium-sized (∼0.01–0.1 km3) but CO2-rich (2 wt%) magma, possibly stored at pressures of ∼100 to 120 MPa. Independent geophysical evidence (e.g., inferred from geodetic and gravity data) is needed to distinguish between these two possibilities.
    Description: Published
    Description: 4153–4169
    Description: 2V. Dinamiche di unrest e scenari pre-eruttivi
    Description: JCR Journal
    Description: restricted
    Keywords: Campi Flegrei ; calderas ; gas output ; 04. Solid Earth::04.08. Volcanology::04.08.01. Gases ; 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::04.08.07. Instruments and techniques ; 04. Solid Earth::04.08. Volcanology::04.08.08. Volcanic risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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