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  • Articles  (186)
  • 04.08. Volcanology  (71)
  • 04.06. Seismology  (57)
  • 04.04. Geology  (29)
  • 04. Solid Earth::04.06. Seismology::04.06.11. Seismic risk  (28)
  • 04. Solid Earth::04.06. Seismology::04.06.03. Earthquake source and dynamics  (25)
  • Creep observations and analysis
  • MDPI  (69)
  • Seismological Society of America  (56)
  • Wiley-AGU  (23)
  • Taylor & Francis  (11)
  • EGU - Copernicus
  • Elsevier B.V.
  • Wiley
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  • 1
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    First In-Situ Measurements of Plume Chemistry at Mount Garet Volcano, Island of Gaua (Vanuatu) (2020)
    MDPI
    Details
    Publication Date: 2020-11-25
    Description: Recent volcanic gas compilations have urged the need to expand in-situ plume measurements to poorly studied, remote volcanic regions. Despite being recognized as one of the main volcanic epicenters on the planet, the Vanuatu arc remains poorly characterized for its subaerial emissions and their chemical imprints. Here, we report on the first plume chemistry data for Mount Garet, on the island of Gaua, one of the few persistent volatile emitters along the Vanuatu arc. Data were collected with a multi-component gas analyzer system (multi-GAS) during a field campaign in December 2018. The average volcanic gas chemistry is characterized by mean molar CO2/SO2, H2O/SO2, H2S/SO2 and H2/SO2 ratios of 0.87, 47.2, 0.13 and 0.01, respectively. Molar proportions in the gas plume are estimated at 95.9 11.6, 1.8 0.5, 2.0 0.01, 0.26 0.02 and 0.06 0.01, for H2O, CO2, SO2, H2S and H2. Using the satellite-based 10-year (2005–2015) averaged SO2 flux of ~434 t d􀀀1 for Mt. Garet, we estimate a total volatile output of about 6482 t d􀀀1 (CO2 ~259 t d􀀀1; H2O ~5758 t d􀀀1; H2S ~30 t d􀀀1; H2 ~0.5 t d􀀀1). This may be representative of a quiescent, yet persistent degassing period at Mt. Garet; whilst, as indicated by SO2 flux reports for the 2009–2010 unrest, emissions can be much higher during eruptive episodes. Our estimated emission rates and gas composition for Mount Garet provide insightful information on volcanic gas signatures in the northernmost part of the Vanuatu Arc Segment. The apparent CO2-poor signature of high-temperature plume degassing at Mount Garet raises questions on the nature of sediments being subducted in this region of the arc and the possible role of the slab as the source of subaerial CO2. In order to better address the dynamics of along-arc volatile recycling, more volcanic gas surveys are needed focusing on northern Vanuatu volcanoes.
    Description: This research was conducted as part of the Trail by Fire II—Closing the Ring Project (PI: Y. Moussallam) funded by the National Geographic Society (grant number CP-122R-17), the Rolex Awards for Enterprise and the French national Research Institute for Development (IRD). J.L. also acknowledges travel funding support from Ministero dell’istruzione, dell’università e della ricerca (MIUR;) under grant n. PRIN2017-2017LMNLAW).
    Description: Published
    Description: id 7293
    Description: 4V. Processi pre-eruttivi
    Description: JCR Journal
    Keywords: Vanuatu ; Gaua ; Mount Garet ; Multi-GAS ; volcanic gas composition ; volatile fluxes ; 04.08. Volcanology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Characterisation of the magmatic signature in gas emissions from Turrialba Volcano, Costa Rica (2020)
    EGU - Copernicus
    Details
    Publication Date: 2020-11-25
    Description: The equilibrium composition of volcanic gaseswith their magma is often overprinted by interaction with ashallow hydrothermal system. Identifying the magmatic sig-nature of volcanic gases is critical to relate their composi-tion to properties of the magma (temperature,fO2, gas-meltsegregation depth). We report measurements of the chemi-cal composition and flux of the major gas species emittedfrom Turrialba Volcano during March 2013. Measurementswere made of two vents in the summit region, one of whichopened in 2010 and the other in 2012. We determined an av-erage SO2flux of 5.2±1.9 kg s−1using scanning ultravio-let spectroscopy, and molar proportions of H2O, CO2, SO2,HCl, CO and H2gases of 94.16, 4.03, 1.56, 0.23, 0.003 and0.009 % respectively by open-path Fourier transform infrared(FTIR) spectrometry and a multi-species gas-sensing system.Together, these data imply fluxes of 88, 8, 0.44, 5×10−3and1×10−3kg s−1for H2O, CO2, HCl, CO and H2respectively.Although H2S was detected, its concentration could not beresolved. HF was not detected. The chemical signature of thegas from both vents was found to be broadly similar. Follow-ing the opening of the 2010 and 2012 vents we found limitedto negligible interaction of the magmatic gas with the hy-drothermal system has occurred and the gas composition ofthe volcanic plume is broadly representative of equilibriumwith the magma. The time evolution of the gas composition,the continuous emission of large quantities of SO2, and thephysical evolution of the summit area with new vent open-ings and more frequent eruptions all point towards a continu-ous drying of the hydrothermal system at Turrialba’s summitat an apparently increasing rate.
    Description: This research was supported by the RoyalGeographical Society (with IBG) with a Geographical FieldworkGrant. Y. Moussallam and N. Peters were additionally supportedby the Philip Lake funds from the Department of Geography,University of Cambridge. Y. Moussallam acknowledges a researchgrant from Mazamas and support through ERC project #279790.We thank the NERC Field Spectroscopy Facility for the loanof their infrared spectrometer. A. Aiuppa acknowledges supportthrough ERC grant no. 305377 (BRIDGE)
    Description: Published
    Description: 1341–1350
    Description: 4V. Processi pre-eruttivi
    Description: JCR Journal
    Keywords: volcanic degassing ; Multi-GAS ; UV spectroscopy ; FTIR ; 04.08. Volcanology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    Strain Pattern and Kinematics of the Canary Islands from GNSS Time Series Analysis (2021)
    MDPI
    Details
    Publication Date: 2021-01-04
    Description: Following the 2004 seismic unrest at Tenerife and the 2011–2012 submarine eruption at El Hierro, the number of Global Navigation Satellite System (GNSS) observation sites in the Canary Islands (Spain) has increased, offering scientists a useful tool with which to infer the kinematics and present-day surface deformation of the Canary sector of the Atlantic Ocean. We take advantage of the common-mode component filtering technique to improve the signal-to-noise ratio of the velocities retrieved from the daily solutions of 18 permanent GNSS stations distributed in the Canaries. The analysis of GNSS time series spanning the period 2011–2017 enabled us to characterize major regions of deformation along the archipelago through the mapping of the 2D infinitesimal strain field. By applying the triangular segmentation approach to GNSS velocities, we unveil a variable kinematic behaviour within the islands. The retrieved extension pattern shows areas of maximum deformation west of Tenerife, Gran Canaria and Fuerteventura. For the submarine main seismogenic fault between Tenerife and Gran Canaria, we simulated the horizontal deformation and strain due to one of the strongest (mbLg 5.2) earthquakes of the region. The seismic areas between islands, mainly offshore Tenerife and Gran Canaria, seem mainly influenced by the regional tectonic stress, not the local volcanic activity. In addition, the analysis of the maximum shear strain confirms that the regional stress field influences the E–W and NE–SW tectonic lineaments, which, in accordance with the extensional and compressional tectonic regimes identified, might favour episodes of volcanism in the Canary Islands.
    Description: Published
    Description: 3297
    Description: 2T. Deformazione crostale attiva
    Description: 6V. Pericolosità vulcanica e contributi alla stima del rischio
    Description: JCR Journal
    Keywords: GNSS time series ; kinematics and ground deformation ; Canary Islands ; 04.02. Exploration geophysics ; 04.03. Geodesy ; 04.07. Tectonophysics ; 04.08. Volcanology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 4
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    New strategies for vertical transport in chemistry transport models: application to the case of the Mount Etna eruption on 18 March 2012 with CHIMERE v2017r4 (2021)
    EGU - Copernicus
    Details
    Publication Date: 2021-01-19
    Description: Excessive numerical diffusion is one of the major limitations in the representation of long-range transport by chemistry transport models. In the present study, we focus on excessive diffusion in the vertical direction, which has been shown to be a major issue, and we explore three possible ways of addressing this problem: increasing the vertical resolution, using an advection scheme with anti-diffusive properties and more accurately representing the vertical wind. This study was carried out using the CHIMERE chemistry transport model for the 18 March 2012 eruption of Mount Etna, which released about 3 kt of sulfur dioxide into the atmosphere in a plume that was observed by satellite instruments (the Infrared Atmospheric Sounding Interferometer instrument, IASI, and the Ozone Monitoring Instrument, OMI) for several days. The change from the classical Van Leer (1977) scheme to the Després and Lagoutière (1999) anti-diffusive scheme in the vertical direction was shown to provide the largest improvement to model outputs in terms of preserving the thin plume emitted by the volcano. To a lesser extent, the improved representation of the vertical wind field was also shown to reduce plume dispersion. Both of these changes helped to reduce vertical diffusion in the model as much as a brute-force approach (increasing vertical resolution).
    Description: Published
    Description: 5707–5723
    Description: 5V. Processi eruttivi e post-eruttivi
    Description: JCR Journal
    Keywords: 04.08. Volcanology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
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    Statistical moments of power spectrum: a fast tool for the classification of seismic events recorded on volcanoes (2021)
    EGU - Copernicus
    Details
    Publication Date: 2021-01-22
    Description: Spectral analysis has been applied to almost thou-sand seismic events recorded at Vesuvius volcano (Naples,southern Italy) in 2018 with the aim to test a new tool fora fast event classification. We computed two spectral pa-rameters, central frequency and shape factor, from the spec-tral moments of order 0, 1, and 2, for each event at sevenseismic stations taking the mean among the three compo-nents of ground motion. The analyzed events consist ofvolcano-tectonic earthquakes, low frequency events and un-classified events (landslides, rockfall, thunders, quarry blasts,etc.). Most of them are of low magnitude, and/or low maxi-mum signal amplitude, therefore the signal to noise ratio isvery different between the low noise summit stations andthe higher noise stations installed at low elevation aroundthe volcano. The results of our analysis show that volcano-tectonic earthquakes and low frequency events are easily dis-tinguishable through the spectral moments values, particu-larly at seismic stations closer to the epicenter. On the con-trary, unclassified events show the spectral parameters valuesdistributed in a broad range which overlap both the volcano-tectonic earthquakes and the low frequency events. Since thecomputation of spectral parameters is extremely easy and fastfor a detected event, it may become an effective tool for eventclassification in observatory practice.
    Description: Published
    Description: 67–74
    Description: 1SR TERREMOTI - Sorveglianza Sismica e Allerta Tsunami
    Description: N/A or not JCR
    Keywords: Vesuvius ; Spectral Analisys ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    Supervised learning (2021)
    Elsevier B.V.
    Details
    Publication Date: 2021-02-01
    Description: In supervised classification, we search criteria allowing us to decide whether a sample belongs to a certain class of patterns. The identification of such decision functions is based on examples where we know a priori to which class they belong. The distinction of seismic signals, produced from earthquakes and nuclear explosions, is a classical problem of discrimination using classification with supervision. We move on from observed data—signals originating from known earthquakes and nuclear tests—and search for criteria on how to assign a class to a signal of unknown origin. We begin with Principal Component Analysis (PCA) and Fisher's Linear Discriminant Analysis (FLDA), identifying a linear element separating groups at best. PCA, FLDA, and likelihood-based approaches make use of statistical properties of the groups. Considering only the number of misclassified samples as a cost, we may prefer alternatives, such as the Multilayer Perceptrons (MLPs). The Support Vector Machines (SVMs) use a modified cost function, combining the criterion of the minimum number of misclassified samples with a request of separating the hulls of the groups with a margin as wide as possible. Both SVMs and MLPs overcome the limits of linear discrimination. A famous example for the advantages of the two techniques is the eXclusive OR (XOR) problem, where we wish to form classes of objects having the same parity—even, e.g., (0,0), (1,1) or odd, e.g., (0,1), (1,0). MLPs and SVMs offer effective methods for the identification of nonlinear decision functions, allowing us to resolve classification problems of any complexity provided the data set used during earning is sufficiently large. In Hidden Markov Models (HMMs), we consider observations where their meaning depends on their context. Observations form a causal chain generated by a hidden process. In Bayesian Networks (BNs) we represent conditional (in)dependencies between a set of random variables by a graphical model. In both HMMs and BNs, we aim at identifying models and parameters that explain observations with a highest possible degree of probability.
    Description: Published
    Description: 33-85
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Keywords: pattern recognition ; supervised learning ; Support Vector Machines ; Multilayer Perceptrons ; Hidden Markov Models ; Bayesian Networks ; 04.04. Geology ; 04.06. Seismology ; 04.07. Tectonophysics ; 04.08. Volcanology ; 05.04. Instrumentation and techniques of general interest
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 7
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    Patterns, objects, and features (2021)
    Elsevier B.V.
    Details
    Publication Date: 2021-02-01
    Description: Patterns and objects are described by a variety of characteristics, namely features and feature vectors. Features can be numerical, ordinal, and categorical. Patterns can be made up of a number of objects, such as in speech processing. In geophysics, numerical features are the most common ones and we focus on those. The choice of appropriate features requires a priori reasoning about the physical relation between patterns and features. We present strategies for feature identification and procedures suitable for pattern recognition. In time series analysis and image processing, the direct use of raw data is not feasible. Procedures of feature extraction, based on locally encountered characteristics of the data, are applied. Here we present the problem of delineating segments of interest in time series and textures in image processing. In transformations, we “translate” our raw data to a form suitable for learning. In Principal Component Analysis, we rotate the original features to a system of uncorrelated variables, limiting redundancy. Independent Component Analysis follows a similar strategy, transforming our data into variables independent of each other. Fourier transform and wavelet transform are based on the representation of the original data as a series of basis functions—sines and cosines or finite-length wavelets. Redundancy reduction is achieved considering the contributions of the single basis functions. Even though a large number of features help to solve a classification problem, feature vectors with high dimensions pose severe problems. Besides the computational burden, we encounter problems known under the term “curse of dimensionality.” The curse of dimensionality entails the necessity of feature selection and reduction, which includes a priori considerations as well as redundancy reduction. The significance of features may be evaluated with tests, such as Student’s t or Hotelling's T2, and, in more complex problems, with cross-validation methods.
    Description: Published
    Description: 3-13
    Description: 5T. Sismologia, geofisica e geologia per l'ingegneria sismica
    Keywords: pattern recognition ; objects ; features ; 04.04. Geology ; 04.06. Seismology ; 04.07. Tectonophysics ; 04.08. Volcanology ; 05.04. Instrumentation and techniques of general interest
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: book chapter
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  • 8
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    Temperature and Emissivity Separation ‘Draping’ Algorithm Applied to Hyperspectral Infrared Data (2021)
    MDPI
    Details
    Publication Date: 2021-02-03
    Description: In the presented work, the spectral emissivity of basaltic melts at magmatic temperatures was retrieved in a laboratory-controlled experiment by measuring their spectral radiance. Granulated bombs of Etnean basalts were melted and the radiant energy from the melting surface was recorded by a portable spectroradiometer in the short wavelength infrared (SWIR) spectral range between 1500 and 2500 nm. The Draping algorithm, an improved algorithm for temperature and emissivity separation, was applied for the first time to SWIR hyperspectral data in order to take into account the non-uniform temperature distribution of the melt surface and, at the same time, solving the two temperatures and the spectral emissivity. The results have been validated by comparing our results with the emissivity measured at a "lava simulator". Basalt spectral emissivity does not vary significantly at magmatic temperature, but shows an absorption feature in the range 2180–2290 nm, an atmospheric window pivotal for the IR remote sensing of active volcanoes
    Description: Published
    Description: 2046
    Description: 5V. Processi eruttivi e post-eruttivi
    Description: JCR Journal
    Keywords: temperature–emissivity separation ; Draping ; thermal remote sensing ; Lab experiment ; 04.08. Volcanology ; solid Earth
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    On the Propagation Path of Magma‐Filled Dikes and Hydrofractures: The Competition Between External Stress, Internal Pressure, and Crack Length (2019)
    Wiley
    Details
    Publication Date: 2021-03-09
    Description: Mixed‐mode fluid‐filled cracks represent a common means of fluid transport within the Earth's crust. They often show complex propagation paths which may be due to interaction with crustal heterogeneities or heterogeneous crustal stress. Previous experimental and numerical studies focus on the interplay between fluid over-pressure and external stress but neglect the effect of other crack parameters. In this study, we address the role of crack length on the propagation paths in the presence of an external heterogeneous stress field. We make use of numerical simulations of magmatic dike and hydrofracture propagation, carried out using a two‐dimensional boundary element model, and analogue experiments of air‐filled crack propagation into a transparent gelatin block. We use a 3‐D finite element model to compute the stress field acting within the gelatin block and perform a quantitative comparison between 2‐D numerical simulations and experiments. We show that, given the same ratio between external stress and fluid pressure, longer fluid‐filled cracks are less sensitive to the background stress, and we quantify this effect on fluid‐filled crack paths. Combining the magnitude of the external stress, the fluid pressure, and the crack length, we define a new parameter, which characterizes two end member scenarios for the propagation path of a fluid‐filled fracture. Our results have important implications for volcanological studies which aim to address the problem of complex trajectories of magmatic dikes (i.e., to forecast scenarios of new vents opening at volcanoes) but also have implications for studies that address the growth and propagation of natural and induced hydrofractures.
    Description: Published
    Description: 2064–2081
    Description: 2V. Struttura e sistema di alimentazione dei vulcani
    Description: JCR Journal
    Keywords: Magmatic dykes ; hydrofractures ; Numerical symulations ; Analogue experiments ; 04.08. Volcanology ; 05.05. Mathematical geophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
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    On the Source Parameters and Genesis of the 2017, Mw 4 Montesano Earthquake in the Outer Border of the Val d’Agri Oilfield (Italy) (2021)
    MDPI
    Details
    Publication Date: 2021-03-24
    Description: On October 27, 2017, an Mw 4 earthquake occurred close to the municipality of Montesano sulla Marcellana, less than 10 km external to the concession of the largest European onshore hydrocarbon reservoir—the Val d’Agri oilfield (Southern Italy). Being a weak event located outside the extended monitoring domain of the industrial concession, the relevance of this earthquake and the possible links with the hydrocarbon exploitation were not extensively discussed. Actually, the analysis of shallow seismic events close to subsurface exploitation domains plays a significant role in the definition of key parameters in order to discriminate between natural, triggered, and induced seismicity, especially in tectonically active regions. The study of weak-to-moderate earthquakes can improve the characterization of the potentially destructive seismic hazard of this particular area, already struck by M 〉 6.5 episodes in the past. In this work, we analyze the source parameters of this Mw 4 earthquake by applying advanced seismological techniques to estimate the uncertainties derived from the moment tensor inversion and identify plausible directivity effects. The moment tensor is dominated by a NW–SE oriented normal faulting with a centroid depth of 14 km. A single ML 2.1 aftershock was recorded and used as the empirical Green’s function to calculate the apparent source time function for the mainshock. Apparent durations (in the range 0.11–0.21 s, obtained from S-waves) define an azimuthal pattern, which reveals an asymmetric bilateral rupture with 70% of the rupture propagation in the N310°Wdirection, suggesting a rupture plane dipping to the SW. Our results tally with the activation of a deeper fault segment associated with the Eastern Agri Fault System close to the basement as the origin of the Montesano earthquake. Finally, the Coulomb stress rate induced by depletion of the oilfield is calculated to quantify the trigger potential estimated for the Montesano earthquake yielding relatively low probabilities below 10%. Our analyses point toward the conclusion that the Mw 4 event was more likely due to the local natural tectonic stress, rather than induced or triggered by the long-term hydrocarbon extraction in the Val d’Agri oilfield.
    Description: Published
    Description: 617794
    Description: 3T. Fisica dei terremoti e Sorgente Sismica
    Description: JCR Journal
    Keywords: earthquake source ; induced seismicity ; directivity ; triggered earthquake ; Val d’Agri oilfield ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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