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  • 04. Solid Earth::04.02. Exploration geophysics::04.02.01. Geochemical exploration
  • 04. Solid Earth::04.05. Geomagnetism::04.05.03. Global and regional models
  • diffuse degassing
  • AGU  (3)
  • Blackwell Science Ltd  (2)
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  • 1
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    Translated origin spherical cap harmonic analysis (2008)
    Blackwell Science Ltd
    Details
    Publication Date: 2017-04-03
    Description: The method of spherical cap harmonic analysis (SCHA), due to Haines (1985) is appropriate for regional geomagnetic field modelling as it includes the required potential field constraints and, for a given number of model parameters, describes shorter wavelength features than a global spherical harmonic model. If the origin of the coordinate system is moved from the centre of the Earth towards the surface then the Earth's surface is no longer equidistant from the origin. At the Earth's surface the minimum wavelength described by a SCH model in the new coordinate system is smaller at the centre of the region than at the edge. This method of translated origin spherical cap harmonic analysis (TOSCA) has been applied to regional field modelling for Italy. The method is able to take advantage of the dense distribution of data at the centre of region and the model effectively smooths towards the periphery. The performance of the TOSCA model is discussed in relation to a model derived using conventional SCHA.
    Description: Published
    Description: 253-263
    Description: N/A or not JCR
    Description: reserved
    Keywords: ground and satellite data analysis ; regional field modelling ; spherical cap harmonic analysis ; 04. Solid Earth::04.05. Geomagnetism::04.05.03. Global and regional models ; 05. General::05.05. Mathematical geophysics::05.05.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    The first Antarctic geomagnetic Reference Model (ARM) (2008)
    AGU
    Details
    Publication Date: 2012-02-03
    Description: Spherical Cap Harmonic Analysis has been applied to obtain a reference model of geomagnetic secular change for Antarctica valid for the last forty years. In this paper, we use the latest available observatory data to update this model and to compare it with the 8th generation IGRF. In addition, the selected set of total field values used for the generation of the Oersted Initial Field Model have been employed together with observatory data to develop the first complete Antarctic Reference Model (ARM). This model improves the fit to the secular variation deduced from observatory data by about 60% relative to IGRF, and the fit to observatory and satellite field data by 8%. The model allows merging data sets taken at different altitudes and epochs in Antarctica, where significant temporal geomagnetic variations occur.
    Description: Published
    Description: 1192
    Description: JCR Journal
    Description: reserved
    Keywords: Geomagnetic reference fields ; Geomagnetic spatial variations (all harmonics and anomalies) ; Geomagnetic time variations - secular and long term ; 04. Solid Earth::04.05. Geomagnetism::04.05.03. Global and regional models ; 04. Solid Earth::04.05. Geomagnetism::04.05.04. Magnetic anomalies ; 04. Solid Earth::04.05. Geomagnetism::04.05.05. Main geomagnetic field
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    Tectonic control over large-scale diffuse degassing in eastern Sicily (Italy) (2005)
    Blackwell Science Ltd
    Details
    Publication Date: 2017-04-04
    Description: Eastern Sicily (southern Italy) is characterised by the presence of many natural gas emissions (mofettes, mud volcanoes). These gases are mostly carbon dioxide and methane, with minor amounts of helium, hydrogen, carbon monoxide and hydrocarbons. In this study, the extent and orientation of soil gas anomalies (He and CO2) were investigated on a wide area (approximately 110 km2) located just SW of Mt. Etna. From a structural point of view, this area lays on a typical foredeep–foreland system that marks the boundary between the southern part of the Eurasian plate and the northern part of the African plate in the central Mediterranean. No tectonic structure was revealed in this area by surface geological surveys. Very high soil emissions were found, and their spatial pattern reveals the existence of some active faults all directed about N508E. This direction coincides with that of two major fault systems that cut eastern Sicily and are evident, respectively, NE and SW of the study area. Soil gas data suggest that these fault systems are the expression of a single continuous structural line which is probably responsible for the past and present magma uprise in eastern Sicily. Isotopic values of carbon of CO2 suggest a minor contribution of organic carbon. Moreover, in the highest degassing sites the isotopic values of He found in association with CO2 (He abundance¼11–70 p.p.m.; R/Ra between 6.0 and 6.2) suggest that both gases are mantle derived. The extent of the areas affected by high gas emissions and the amounts of deep CO2 emitted in the investigated area (several hundred tonnes per day) may provide additional supporting evidence of a mantle upwelling taking place beneath this region.
    Description: Gruppo Nazionale per la Vulcanologia Italy.
    Description: Published
    Description: 273–284
    Description: partially_open
    Keywords: CO2 ; diffuse degassing ; Sicily ; 04. Solid Earth::04.02. Exploration geophysics::04.02.01. Geochemical exploration ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 597 bytes
    Format: 866788 bytes
    Format: text/html
    Format: application/pdf
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  • 4
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    Geomagnetic jerks in the polar regions (2009)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: The occurrence of geomagnetic jerks over the Arctic and Antarctic regions is here investigated. Maps of geomagnetic secular acceleration over the polar regions are produced from the CM4 and CHAOS models and the occurrence of geomagnetic jerks is associated with jumps in secular acceleration. The obtained results confirm that in Antarctica geomagnetic jerks systematically follow geomagnetic jerks in the Arctic region with a time delay from one to three years. Evidence is found of an abrupt change in secular acceleration in both polar regions around 1985, suggesting that the 1985 local jerk could actually be a worldwide event. Combining our results with the results previously obtained on the occurrence of a geomagnetic jerk at low-mid latitudes around 2003, we support the hypothesis of a global extension of an event occurred at the beginning of the 21st century.
    Description: Published
    Description: L15304
    Description: 3.4. Geomagnetismo
    Description: JCR Journal
    Description: reserved
    Keywords: geomagnetic jerks ; magnetic global models ; geomagnetic secular variation ; 04. Solid Earth::04.05. Geomagnetism::04.05.02. Geomagnetic field variations and reversals ; 04. Solid Earth::04.05. Geomagnetism::04.05.03. Global and regional models ; 04. Solid Earth::04.05. Geomagnetism::04.05.05. Main geomagnetic field
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
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    Hydrogen in the gas plume of an open‐vent volcano, Mount Etna, Italy (2011)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: We report here on the first hydrogen determinations in the volcanic gas plume of Mount Etna, in Italy, which we obtained during periodic field surveys on the volcano’s summit area with an upgraded MultiGAS. Using a specific (EZT3HYT) electrochemical sensor, we resolved H2 concentrations in the plume of 1–3 ppm above ambient (background) atmosphere and derived H2‐SO2 and H2‐H2O plume molar ratios of 0.002–0.044 (mean 0.013) and 0.0001–0.0042 (mean 0.0018), respectively. Taking the above H2‐SO2 ratios in combination with a time‐averaged SO2 flux of 1600 Gg yr−1, we evaluate that Etna contributes a time‐averaged H2 flux of ∼0.65 Gg yr−1, suggesting that the volcanogenic contribution to the global atmospheric H2 budget (70,000–100,000 Gg yr−1) is marginal. We also use our observed H2‐H2O ratios to propose that Etna’s passive plume composition is (at least partially) representative of a quenched (temperatures between 750°C and 950°C) equilibrium in the gas‐magma system, at redox conditions close to the nickel‐nickel oxide (NNO) mineral buffer. The positive dependence between H2‐SO2, H2‐H2O, and CO2‐SO2 ratios suggests that H2 is likely supplied (at least in part) by deeply rising CO2‐rich gas bubbles, fluxing through a CO2‐depleted shallow conduit magma.
    Description: Published
    Description: B10204
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: 2.4. TTC - Laboratori di geochimica dei fluidi
    Description: JCR Journal
    Description: restricted
    Keywords: Hydrogen ; Mount Etna ; Open-vent volcano ; plume ; 01. Atmosphere::01.01. Atmosphere::01.01.07. Volcanic effects ; 04. Solid Earth::04.02. Exploration geophysics::04.02.01. Geochemical exploration ; 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
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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