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  • American Geophysical Union  (5,217)
  • American Association for the Advancement of Science  (4,751)
  • 2005-2009  (9,968)
  • 1980-1984
  • 2009  (9,968)
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Keywords
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  • 2005-2009  (9,968)
  • 1980-1984
Year
  • 1
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    Hindcasting of decadal-timescale estuarine bathymetric change with a tidal-timescale model (2009)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: This paper is not subject to U.S. copyright. The definitive version was published in Journal of Geophysical Research 114 (2009): F04019, doi:10.1029/2008JF001191.
    Description: Hindcasting decadal-timescale bathymetric change in estuaries is prone to error due to limited data for initial conditions, boundary forcing, and calibration; computational limitations further hinder efforts. We developed and calibrated a tidal-timescale model to bathymetric change in Suisun Bay, California, over the 1867–1887 period. A general, multiple-timescale calibration ensured robustness over all timescales; two input reduction methods, the morphological hydrograph and the morphological acceleration factor, were applied at the decadal timescale. The model was calibrated to net bathymetric change in the entire basin; average error for bathymetric change over individual depth ranges was 37%. On a model cell-by-cell basis, performance for spatial amplitude correlation was poor over the majority of the domain, though spatial phase correlation was better, with 61% of the domain correctly indicated as erosional or depositional. Poor agreement was likely caused by the specification of initial bed composition, which was unknown during the 1867–1887 period. Cross-sectional bathymetric change between channels and flats, driven primarily by wind wave resuspension, was modeled with higher skill than longitudinal change, which is driven in part by gravitational circulation. The accelerated response of depth may have prevented gravitational circulation from being represented properly. As performance criteria became more stringent in a spatial sense, the error of the model increased. While these methods are useful for estimating basin-scale sedimentation changes, they may not be suitable for predicting specific locations of erosion or deposition. They do, however, provide a foundation for realistic estuarine geomorphic modeling applications.
    Description: This study was supported by the U.S. Geological Survey’s Priority Ecosystems Science program, CALFED Bay/Delta Program, and the University of California Center for Water Resources. Use of ROMS and the CSTMS was supported by the U.S. Geological Survey, with assistance from John Warner.
    Keywords: Estuarine geomorphology ; Numerical modeling ; Sediment transport
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 2
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    Sea-floor spreading initiation: constraints from geophysical data of the Thetis Deep, northern Red Sea (2009)
    American Geophysical Union
    Details
    Publication Date: 2021-07-14
    Description: A major step in the "Wilson Cycle" is the splitting of a continent and the birth of a new ocean, with the consequent formation of passive plate margins. The transition from a continental to an oceanic rift can be observed today nowhere better than in the Red Sea/Gulf of Aden system. We have carried out during several years a number of expeditions in the axial portion of the Northern Red Sea, in the region where the northernmost nuclei of axial emplacement of oceanic crust can be observed. High resolution multibeam, magnetics, gravity and multichannel seismic reflection surveys from the Thetis Deep revealed rates and modes of initial pulses of sea floor spreading, velocity of S to N axial propagation of the oceanic rift, evolution of initial MORB-type crust and nature of the mantle thermal anomaly that caused the transition from a continental to an oceanic rift. The Thetis deep is made of three en echelon fault-bounded axial basins that are joined together with axial volcanic ridges and a large number of scattered small central volcanoes. The southern basin shows a strong linear magnetic anomaly corresponding to the axial neo-volcanic zone. Two negative symmetric anomalies identified as Matuyama are present in the southernmost part of this basin, suggesting that the emplacement of oceanic crust at this site started roughly 2.5 Ma, with an average half spreading rate of 6 mm/yr. The central sub-basin is also characterized by a strongly magnetic linear neo- volcanic zone that, however, is flanked only by a small, "vanishing" symmetrical negative anomaly suggesting emplacement of oceanic crust not earlier than about 1 Ma. The northern sub-basin does not show a clearly defined linear neo-volcanic zone although it displays a strong central magnetization suggesting initial emplacement of oceanic crust 〈 0.7 Ma. This pattern implies a south to north time progression of the initial emplacement of oceanic crust within the Thetis system, with a propagation rate of about 20 mm/yr. Gravity data inversions constrained by seismic data reveal that the oceanic crust extends from the axial neo-volcanic ridges toward the master faults of the axial depression with crustal thickness ranging from 4 to 6 km. The increasing thickness of basaltic crust toward the edges of the basin together with higher degree of melting, inferred by the geochemistry of the basaltic glasses, and higher central magnetization of the northernmost and youngest basin suggest a pulse of faster spreading rate at the onset of sea-floor spreading.
    Description: Published
    Description: San Francisco
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: open
    Keywords: Spatial variations attributed to seafloor spreading ; Oceanic crust ; Seafloor morphology, geology, and geophysics ; Mid-ocean ridges ; 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes ; 04. Solid Earth::04.01. Earth Interior::04.01.03. Mantle and Core dynamics ; 04. Solid Earth::04.02. Exploration geophysics::04.02.04. Magnetic and electrical methods
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Oral presentation
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  • 3
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    Partitioning Recent Greenland Mass Loss (2009)
    American Association for the Advancement of Science
    In:  Science, 326 (5955). pp. 984-986.
    Details
    Publication Date: 2020-05-28
    Description: Mass budget calculations, validated with satellite gravity observations [from the Gravity Recovery and Climate Experiment (GRACE) satellites], enable us to quantify the individual components of recent Greenland mass loss. The total 2000–2008 mass loss of ~1500 gigatons, equivalent to 0.46 millimeters per year of global sea level rise, is equally split between surface processes (runoff and precipitation) and ice dynamics. Without the moderating effects of increased snowfall and refreezing, post-1996 Greenland ice sheet mass losses would have been 100% higher. Since 2006, high summer melt rates have increased Greenland ice sheet mass loss to 273 gigatons per year (0.75 millimeters per year of equivalent sea level rise). The seasonal cycle in surface mass balance fully accounts for detrended GRACE mass variations, confirming insignificant subannual variation in ice sheet discharge.
    Type: Article , PeerReviewed
    Format: text
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  • 4
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    On the onset of the ice phase in boundary layer Arctic clouds (2009)
    American Geophysical Union
    In:  EPIC3J. Geophys. Res., 114, D19201, 114, D19201., American Geophysical Union, 114
    Details
    Publication Date: 2017-10-20
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 5
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    Earth's Degassing: A Missing Ethane and Propane Source (2009)
    American Association for the Advancement of Science
    Details
    Publication Date: 2017-04-04
    Description: BREVIA
    Description: Current emission inventories require an additional "unknown" source to balance the global atmospheric budgets of ethane (C2H6). Here, we provide evidence that a substantial part of the missing source can be attributed to natural gas seepage from petroliferous, geothermal, and volcanic areas. Such geologic sources also inject propane (C3H8) into the atmosphere. The analysis of a large data set of methane (CH4), ethane, and propane concentrations in surface gas emissions of 238 sites from different geographic and geologic areas, coupled with published estimates of geomethane emissions, suggests that Earth's degassing accounts for at least 17% and 10% of total ethane and propane emissions, respectively.
    Description: Published
    Description: 478
    Description: 3.8. Geofisica per l'ambiente
    Description: JCR Journal
    Description: reserved
    Keywords: Ethane ; Propane ; Geologic emissions ; Seepage ; 03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
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    A multiparameter approach to volcano monitoring based on 4D analyses of seismo-volcanic and acoustic signals: The 2008 Mt. Etna eruption (2009)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Volcanic tremor and low frequency events, together with infrasound signals, can represent important precursory phenomena of eruptive activity because of their strict relationship with eruptive mechanisms and with fluid flows through the volcano's feeding system. Important variations of these seismo-volcanic and infrasound signals, recorded at Mt. Etna volcano, occurred both in the medium- and short-term before the eruption, that took place on 13 May 2008. The most significant changes were observed in the frequency content and location of LP events, as well as in volcanic tremor location, that allowed us to track the magma pathway feeding the 2008 eruptive activity. The infrasound showed three different families of events linked to the activity of the three active vents: North-East crater, South-East crater and the eruptive fissure. The seismic and infrasonic variations reported, corroborated by ground deformations variations, help to develop a quantitative prediction and early-warning system for effusive and or explosive eruptions.
    Description: European Union VOLUME FP6-2004-Global-3
    Description: Published
    Description: L18307
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Mt. Etna Eruption ; volcano seismology ; 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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    Tracking eruptive phenomena by infrasound: May 13, 2008 eruption at Mt. Etna (2009)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Active volcanoes produce inaudible infrasound due to the coupling between surface magmatic processes and the atmosphere. Monitoring techniques based on infrasound measurements have been proved capable of producing information during volcanic crises. We report observations collected from an infrasound network on Mt. Etna which enabled us to detect and locate a new summit eruption on May 13, 2008 when poor weather inhibited direct observations. Three families of signals were identified that allowed the evolution of the eruption to be accurately tracked in real-time. Each family is representative of a different active vent, producing different waveforms due to their varying geometry. Several competitive models have been developed to explain the source mechanisms of the infrasonic events, but according to our studies we demonstrate that two source models coexist at Mt. Etna during the investigated period. Such a monitoring system represents a breakthrough in the ability to monitor and understand volcanic phenomena.
    Description: Published
    Description: L05304
    Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
    Description: JCR Journal
    Description: reserved
    Keywords: Mt. Etna ; infrasound ; eruption ; volcano monitoring ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Conduit flow experiments help constraining the regime of explosive eruptions (2009)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Accepted for publication in (Geophysical Research Letters). Copyright (2009) American Geophysical Union.
    Description: It is currently impractical to measure what happens in a volcano during an explosive eruption, and up to now much of our knowledge depends on theoretical models. Here we show, by means of large-scale experiments, that the regime of explosive events can be constrained based on the characteristics of magma at the point of fragmentation and conduit geometry. Our model, whose results are consistent with the literature, is a simple tool for defining the conditions at conduit exit that control the most hazardous volcanic regimes. Besides the well-known convective plume regime, which generates pyroclastic fallout, and the vertically collapsing column regime, which leads to pyroclastic flows, we introduce an additional regime of radially expanding columns, which form when the eruptive gas-particle mixture exits from the vent at overpressure with respect to atmosphere. As a consequence of the radial expansion, a dilute collapse occurs, which favours the formation of density currents resembling natural base surges. We conclude that a quantitative knowledge of magma fragmentation, i.e. particle size, fragmentation energy and fragmentation speed, is critical for determining the eruption regime.
    Description: Research was partially funded by DPC-INGV agreement 07-09 and MUR PRIN 06
    Description: In press
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: JCR Journal
    Description: open
    Keywords: explosive eruptions ; 04. Solid Earth::04.08. Volcanology::04.08.02. Experimental volcanism
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    Evidences for strong directional resonances in intensely deformed zones of the Pernicana fault, Mount Etna, Italy (2009)
    American Geophysical Union
    In:  An edited version of this paper was published by AGU. Copyright (2009) American Geophysical Union.
    Details
    Publication Date: 2017-04-04
    Description: In this paper we investigate ground motion properties in the western part of the Pernicana fault. This is the major fault of Mount Etna and drives the dynamic evolution of the area. In a previous work, Rigano et al. (2008) showed that a significant horizontal polarization characterizes ground motion in fault zones of Mount Etna, both during earthquakes and ambient vibrations. We have performed denser microtremor measurements in the NE rift segment and in intensely deformed zones of the Pernicana fault at Piano Pernicana. This study includes mapping of azimuth-dependent horizontal-to-vertical spectral ratios along and across the fault, frequency–wave number techniques applied to array data to investigate the nature of ambient vibrations, and polarization analysis through the conventional covariance matrix method. Our results indicate that microtremors are likely composed of volcanic tremor. Spectral ratios show strong directional resonances of horizontal components around 1 Hz when measurements enter the most damaged part of the fault zone. Their polarization directions show an abrupt change, by 20° to 40°, at close measurements between the northern and southern part of the fault zone. Recordings of local earthquakes at one site in the fault zone confirm the occurrence of polarization with the same angle found using volcanic tremor. We have also found that the directional effect is not time-dependent, at least at a seasonal scale. This observation and the similar behavior of volcanic tremors and earthquake-induced ground motions suggest that horizontal polarization is the effect of local fault properties. However, the 1-Hz resonant frequency cannot be reproduced using the 1-D vertically varying model inferred from the array data analysis, suggesting a role of lateral variations of the fault zone. Although the actual cause of polarization is unknown, a role of stress-induced anisotropy and microfracture orientation in the near-surface lavas of the Pernicana fault can be hypothesized consistently with the sharp rotation of the polarization angle within the damaged fault zone.
    Description: Published
    Description: B10308
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: open
    Keywords: Pernicana fault, fault zone, volcanic tremor, polarization, directional resonance ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
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    Deformation and eruptions at Mt. Etna (Italy): A lesson from 15 years of observations (2009)
    American Geophysical Union
    Details
    Publication Date: 2017-04-04
    Description: Volcanoes deform as a consequence of the rise and storage of magma; once magma reaches a critical pressure, an eruption occurs. However, how the edifice deformation relates to its eruptive behavior is poorly known. Here, we produce a joint interpretation of spaceborne InSAR deformation measurements and volcanic activity at Mt. Etna (Italy), between 1992 and 2006. We distinguish two volcano-tectonic behaviors. Between 1993 and 2000, Etna inflated with a starting deformation rate of 1 cm yr 1 that progressively reduced with time, nearly vanishing between 1998 and 2000; moreover, low-eruptive rate summit eruptions occurred, punctuated by lava fountains. Between 2001 and 2005, Etna deflated, feeding higher-eruptive rate flank eruptions, along with large displacements of the entire East-flank. These two behaviors, we suggest, result from the higher rate of magma stored between 1993 and June 2001, which triggered the emplacement of the dike responsible for the 2001 and 2002–2003 eruptions. Our results clearly show that the joint interpretation of volcano deformation and stored magma rates may be crucial in identifying impending volcanic eruptions.
    Description: This work was partly funded by INGV and the Italian DPC and was supported by ASI, the Preview Project and CRdC-AMRA. DPC-INGV Flank project providing the funds for the publication fees.
    Description: Published
    Description: L02309
    Description: 1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
    Description: 1.5. TTC - Sorveglianza dell'attività eruttiva dei vulcani
    Description: 1.10. TTC - Telerilevamento
    Description: 3.6. Fisica del vulcanismo
    Description: 4.3. TTC - Scenari di pericolosità vulcanica
    Description: 4.5. Degassamento naturale
    Description: JCR Journal
    Description: partially_open
    Keywords: deformation ; eruptions ; Mt. Etna ; eruptive cycle ; InSAR ; 04. Solid Earth::04.01. Earth Interior::04.01.99. General or miscellaneous ; 04. Solid Earth::04.01. Earth Interior::04.01.02. Geological and geophysical evidences of deep processes ; 04. Solid Earth::04.03. Geodesy::04.03.99. General or miscellaneous ; 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::04.04. Geology::04.04.99. General or miscellaneous ; 04. Solid Earth::04.04. Geology::04.04.09. Structural geology ; 04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry ; 04. Solid Earth::04.07. Tectonophysics::04.07.99. General or miscellaneous ; 04. Solid Earth::04.07. Tectonophysics::04.07.02. Geodynamics ; 04. Solid Earth::04.07. Tectonophysics::04.07.07. Tectonics ; 04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous ; 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 ; 05. General::05.02. Data dissemination::05.02.03. Volcanic eruptions
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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