G. Bortoluzzi

Virginia Institute of Marine Science, Abingdon, Virginia, United States

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Publications (66)87.03 Total impact

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    ABSTRACT: An updated bathy-morphological setting of the Aeolian Islands is presented, based on new detailed bathymetric maps of the western, central and eastern sectors of the archipelago. In recent years, the acquisition of multibeam swath bathymetry has greatly expanded knowledge of the submarine portions of the Aeolian volcanic edifices, revealing that their submarine extension is much wider than that of the islands. Indications given by the submarine setting are fundamental for better understanding of the evolution of volcanism and the control exerted by main structural lineaments, as well as to locate large-scale flank instability events and recent submarine eruptive activity.
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    ABSTRACT: An updated bathy-morphological setting of the Aeolian Islands is presented, based on new detailed bathymetric maps of the western, central and eastern sectors of the archipelago. In recent years, the acquisition of multibeam swath bathymetry has greatly expanded knowledge of the submarine portions of the Aeolian volcanic edifices, revealing that their submarine extension is much wider than that of the islands. Indications given by the submarine setting are fundamental for better understanding of the evolution of volcanism and the control exerted by main structural lineaments, as well as to locate large-scale flank instability events and recent submarine eruptive activity.
    10/2013: pages 27-36; , ISBN: 978-186239-365-3
  • tobia tudino, giovanni bortoluzzi, stefano aliani
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    ABSTRACT: Marine water dynamics in the near field of a massive gas eruption near Panarea (Aeolian Islands volcanic arc, SE Tyrrhenian Sea) is described. ADCP current-meters were deployed during the paroxysmal phase in 2002 and 2003 a few meters from the degassing vent, recording day-long time series. Datasets were sorted to remove errors and select good quality ensembles over the entire water column. Standard deviation of error velocity was considered a proxy for inhomogeneous velocity fields over beams. Time series intervals had been selected when the basic ADCP assumptions were fulfilled and random errors minimized. Backscatter data were also proc- essed to identify bubbles in the water column with the aim of locating bubble-free ensembles. Reliable time series are selected combining these data. Two possible scenarios have been described: firstly, a highly dynamic situation with visible surface diverging rings of waves, entrainment on the lower part of the gas column, detrainment in the upper part and a stagnation line (SL) at mid depth where currents were close to zero and most of the gas bubbles spread laterally; secondly, a less dynamic situation with water entraining into the gas plume at all depths and no surface rings of diverging waves. Reasons for these different dynamics may be ascribed to changes in gas fluxes (one order of magnitude higher in 2002). Description of SL is important to quantify its position in the water column and timing for entrainment–detrainment, and it can be measured by ADCP and calculated from models.
    Journal of Marine Systems 01/2013; · 2.66 Impact Factor
  • T. Tudino, G. Bortoluzzi, S. Aliani
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    ABSTRACT: Marine water dynamics in the near field of a massive gas eruption near Panarea (Aeolian Islands volcanic arc, SE Tyrrhenian Sea) is described. ADCP current-meters were deployed during the paroxysmal phase in 2002 and 2003 a few meters from the degassing vent, recording day-long time series. Datasets were sorted to remove errors and select good quality ensembles over the entire water column. Standard deviation of error velocity was considered a proxy for inhomogeneous velocity fields over beams. Time series intervals had been selected when the basic ADCP assumptions were fulfilled and random errors minimized. Backscatter data were also processed to identify bubbles in the water column with the aim of locating bubble-free ensembles. Reliable time series are selected combining these data. Two possible scenarios have been described: firstly, a highly dynamic situation with visible surface diverging rings of waves, entrainment on the lower part of the gas column, detrainment in the upper part and a stagnation line (SL) at mid depth where currents were close to zero and most of the gas bubbles spread laterally; secondly, a less dynamic situation with water entraining into the gas plume at all depths and no surface rings of diverging waves. Reasons for these different dynamics may be ascribed to changes in gas fluxes (one order of magnitude higher in 2002). Description of SL is important to quantify its position in the water column and timing for entrainment–detrainment, and it can be measured by ADCP and calculated from models.
    Journal of Marine Systems 01/2013; · 2.66 Impact Factor
  • Journal of Geophysical Research (Oceans). 01/2013; 118(1):166-183.
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    ABSTRACT: A hierarchy of medium (2 km) and high (0.5 km) resolution operational models cast in the Adriatic sea (NE Mediterranean Sea), relying on an updated core w.r.t. previously existing one, characterized by having a wide variety of applications ranging from civil protection to scientific ones, is presented and described. The computing core of the system sits at Hydro-Meteo-Clima Service (SIMC, Bologna), and the scientific supervision is provided by DISVA Polytechnic University of Marche and CNR-ISMAR Venice. The core of the operational system is based on the Regional Ocean Modeling System, version 3.4. The hydrodynamic variables (e.g. sea surface elevation, currents, temperature, salinity, storm surge height), and wave parameters are predicted every day for the next 72 hours. The surface forcing for the hydrodynamic (AdriaROMS 4.0) and wave (SWAN) operational models is derived from the predicted results of the operational meteorological model COSMO-I7 (7 km resolution) which forecasts atmospheric fields over the whole Italian seas. Hydrodynamic results are verified against oceanographic and wave buoys, tide gauges, bottom mounted acoustic current meter profilers, available in the coastal waters of the Adriatic Sea and oceanographic surveys. More specifically, CNR-ISMAR in the northern Adriatic Sea manages a meteo-oceanographic buoy network and the fixed ocean observatory tower “Acqua Alta”, SIMC manages a wave buoy. Aiming to obtain forecast improvements in coastal areas of northern Adriatic Sea, a newly implemented, more resolved (0.5 km) ROMS version two-way coupled with SWAN is nested in the operational AdriaROMS 4.0 covering the Adriatic Sea at 2 km horizontal resolution. Outputs of operational models drive dedicated submodels for oil-spill transport and dispersion, coastal morphodymanic, sediment transport, saline wedge, water quality.
    OCEANS - Bergen, 2013 MTS/IEEE; 01/2013
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    ABSTRACT: The Messina Strait, that separates peninsular Italy from Sicily, is one of the most seismically active areas of the Mediterranean. The structure and seismotectonic setting of the region are poorly understood, although the area is highly populated and important infrastructures are planned there. New seismic reflection data have identified a number of faults, as well as a crustal scale NE-trending anticline few km north of the strait. These features are interpreted as due to active right-lateral transpression along the north-eastern Sicilian offshore, coexisting with extensional and right-lateral transtensional tectonics in the southern Messina Strait. This complex tectonic network appears to be controlled by independent and overlapping tectonic settings, due to the presence of a diffuse transfer zone between the SE-ward retreating Calabria subduction zone relative to slab advance in the western Sicilian side.
    Scientific Reports 12/2012; 2:970. · 2.93 Impact Factor
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    ABSTRACT: We obtained areal variations of crustal thickness, magnetic intensity, and degree of melting of the sub-axial upwelling mantle at Thetis and Nereus Deeps, the two northernmost axial segments of initial oceanic crustal accretion in the Red Sea, where Arabia is separating from Africa. The initial emplacement of oceanic crust occurred at South Thetis and Central Nereus roughly ∼2.2 and ∼2 Ma, respectively, and is taking place today in the northern Thetis and southern Nereus tips. Basaltic glasses major and trace element composition suggests a rift-to-drift transition marked by magmatic activity with typical MORB signature, with no contamination by continental lithosphere, but with slight differences in mantle source composition and/or potential temperature between Thetis and Nereus. Eruption rate, spreading rate, magnetic intensity, crustal thickness and degree of mantle melting were highest at both Thetis and Nereus in the very initial phases of oceanic crust accretion, immediately after continental breakup, probably due to fast mantle upwelling enhanced by an initially strong horizontal thermal gradient. This is consistent with a rift model where the lower continental lithosphere has been replaced by upwelling asthenosphere before continental rupturing, implying depth-dependent extension due to decoupling between the upper and lower lithosphere with mantle-lithosphere-necking breakup before crustal-necking breakup. Independent along-axis centers of upwelling form at the rifting stage just before oceanic crust accretion, with buoyancy-driven convection within a hot, low viscosity asthenosphere. Each initial axial cell taps a different asthenospheric source and serves as nucleus for axial propagation of oceanic accretion, resulting in linear segments of spreading.
    Geochemistry Geophysics Geosystems 08/2012; 13(8):Q08009. · 2.94 Impact Factor
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    ABSTRACT: The impact of tides in the circulation of the Adriatic sea has been investigated by means of a nested baroclinic numerical ocean model. Tides have been introduced using a modified Flather boundary condition at the open side of the domain. The results show that tidal amplitudes and phases are reproduced correctly by the baroclinic model and the tidal harmonic constants errors are comparable with those resulting from the most consolidated barotropic models. Numerical experiments were conducted to estimate and assess the impact of (i) the modified Flather lateral boundary condition, (ii) the tides on temperature, salinity and stratification structures in the basin, and (iii) the tides on mixing and circulation in general. Tides induce a different momentum advective component in the basin which in turn produces a different distribution of water masses in the basin. Tides impact on mixing and stratification in the Po river region (north-western Adriatic) and induce fluctuations of salinity and temperature on semidiurnal frequencies in all seasons for the first and only winter for the second.
    04/2012;
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    ABSTRACT: We present the preliminary results of a marine high-resolution magnetic and gravity survey of Panarea and Stromboli (Aeolian Islands, cruise R/V Urania PANSTR-2010), in the active, eastern sector of the volcanic arc in the Southern Tyrrhenian Sea (Italy). The Aeolian Arc can be subdivided into western, central and eastern sectors characterized by different structural and volcanological features and evolution. The eastern sector includes the two major volcanic edifices of Panarea and Stromboli. Active volcanism occurs at Stromboli with explosive eruptions and at Panarea with fumaroles and submarine degassing, including the recent, large burst of November 22nd 2002, that lasted several months with a consistent and sustained flux of CO2-dominated gas , orders of magnitude above the steady-state activity. On February 2010 a detailed network of sea-surface gravity (Microg LaCoste Air Sea S-54 model) and magnetic data (Marine Magnetics SeaSPY) were collected with line spacing of 500 m offshore Panarea and Stromboli, including a more detailed acquisition pattern around Panarea with 120 m spacing. Geophysical data acquired offshore Panarea and Stromboli provide a new insight into the deep crustal setting of these volcanic edifices. Low-frequency magnetic anomaly and positive complete Bouguer anomaly identify an intriguing local variation of the crustal properties in this area. Particular attention was drawn to the high-resolution data obtained in the area of the Islets (Lisca Nera, Lisca Bianca, Bottaro, Panarelli, Dattilo) located East of Panarea, where the last 2002 exhalative gas-crisis occurred. The comparison of the data sets of 2002, 2006 and 2010 showed variations of the magnetic properties, reflecting the modification of shallow crustal features and providing information on the hydrothermal system and the structural style of the area. In detail, analysis of new marine gravity data pointed to a local variation of density in the 2002 degassing area (between Dattilo and Lisca Bianca) with a sharp separation, in term of density properties, between the western group of islets and the eastern one. This differentiation seems not correlated to a variation of lithologies in the area, but it suggests the occurrence of local variation of density and/or of a thermal gradient between the two groups of islets. The contrasting structural setting of the eastern and western area of the Islets is also suggested by available GPS geodetic measurements. Detailed strain-rate analyses have been performed showing local, different deformation patterns.
    AGU Fall Meeting Abstracts. 12/2011;
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    ABSTRACT: [1] Reliable piercing points on both sides of the Sea of Marmara enabled us to obtain an estimate of the slip-rate over time scales of 10–15 ka on different fault strands of the North Anatolian Fault (NAF) system. We analyzed geomorphic features in the gulfs of Izmit, Gemlik (Sea of Marmara) and Saros (NE Aegean Sea), which were passively displaced by the NAF strands after their abandonment related to the post-glacial sea level rise. Results for the main northern strand, consistently similar on both sides of the Marmara pull-apart, are in the order of 10 mm/yr, about one half of that expected from geodetic measurements and accepted plate-tectonic models. In the southern branch of the NAF, the estimated rate of ∼4 mm/yr is only slightly higher than that given by geodetic models. Our findings have implications for both neo-tectonic reconstructions of the submerged portion of the NAF system, and fault interactions and seismic hazard estimates in the Marmara region. They suggest that, either the total Anatolia/Eurasia plate motion is more diffuse than previously reported, or geodetic data are not representative of the geological time-scale deformations. Moreover, they suggest that a significant amount of stress is accommodated along the southern strand of the NAF system, on which the last large (M ≈ 7) earthquakes dates back to 1419, 1855 and 1863 AD.
    Tectonics. 12/2011; 30(6).
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    ABSTRACT: The 500 m.y. cycle whereby continents assemble in a single supercontinent and then fragment and disperse again involves the rupturing of a continent and the birth of a new ocean, with the formation of passive plate margins. This process is well displayed today in the Red Sea, where Arabia is separating from Africa. We carried out geophysical surveys and bottom rock sampling in the two Red Sea northernmost axial segments of initial oceanic crust accretion, Thetis and Nereus. Areal variations of crustal thickness, magnetic intensity, and degree of melting of the subaxial upwelling mantle reveal an initial burst of active oceanic crust generation and rapid seafloor spreading below each cell, occurring as soon as the lid of continental lithosphere breaks. This initial pulse may be caused by edge-driven subrift mantle convection, triggered by a strong horizontal thermal gradient between the cold continental lithosphere and the hot ascending asthenosphere. The thermal gradient weakens as the oceanic rift widens; therefore the initial active pulse fades into steady, more passive crustal accretion, with slower spreading and along axis rift propagation.
    Geology 11/2011; 39:1019-1022. · 4.09 Impact Factor
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    ABSTRACT: Panarea and surrounding Islets form a volcanic edifice, that is part of the Eastern sector of the Aeolian Arc, Southern Tyrrhenian Sea. It is now considered inactive, since last documented activity is 20 Ka old. However, on 2002-11-03, gas started to flow violently from the seafloor in an area E of the Island, mainly along NE and NW structural lineaments, and lasting up to 2003-2004 with a consistent flux, orders of magnitude larger that ’steady-state’ fumarolic activity documented there in historical times. On the same period a strong effusive activity of Stromboli (10 NM to NNE) was present. Since then, several investigations have been conducted at sea and on land, with the aim of focusing on the problem of effusive activity at sea, mainly in the light of volcanic surveillance and risk. Among these investigations, some of which have been repeated over years, we present and discuss some data and results from: (a)visual inspection and sampling by divers and ROV, (b)GPS networks and mapping by multibeam and LIDAR, (c) oceanographical measurements by current meters and CTD, and water flux and dynamics measurements, (d)magnetic and gravimetric surveys, (e) multichannel reflection Seismic with OBS and land station networks. Data were used for compilation of high resolution bathymetric, magnetic and gravimetric maps, including the emerged and submerged portions of the edifice.
    06/2011: pages 1468-1486; , ISBN: ISSN 2239-5172
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    ABSTRACT: In September 2008, an expedition of the RV Urania was devoted to exploration of the genomic richness of deep hypersaline anoxic lakes (DHALs) located in the Western part of the Mediterranean Ridge. Approximately 40 nautical miles SE from Urania Lake, the presence of anoxic hypersaline lake, which we named Thetis, was confirmed by swath bathymetry profiling and through immediate sampling casts. The brine surface of the Thetis Lake is located at a depth of 3258 m with a thickness of ≈ 157 m. Brine composition was found to be thalassohaline, saturated by NaCl with a total salinity of 348‰, which is one of highest value reported for DHALs. Similarly to other Mediterranean DHALs, seawater-brine interface of Thetis represents a steep pycno- and chemocline with gradients of salinity, electron donors and acceptors and posseses a remarkable stratification of prokaryotic communities, observed to be more metabolically active in the upper interface where redox gradient was sharper. [(14) C]-bicarbonate fixation analysis revealed that microbial communities are sustained by sulfur-oxidizing chemolithoautotrophic primary producers that thrive within upper interface. Besides microaerophilic autotrophy, heterotrophic sulfate reduction, methanogenesis and anaerobic methane oxidation are likely the predominant processes driving the ecosystem of Thetis Lake.
    Environmental Microbiology 04/2011; 13(8):2250-68. · 5.76 Impact Factor
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    ABSTRACT: Reliable piercing points on both sides of the Sea of Marmara enabled us to obtain an estimate of the slip-rate over time scales of 10-15 ka on different fault strands of the North Anatolian Fault (NAF) system. We analyzed geomorphic features in the gulfs of Izmit, Gemlik (Sea of Marmara) and Saros (NE Aegean Sea), which were passively displaced by the NAF strands after their abandonment related to the post-glacial sea level rise. Results for the main northern strand, consistently similar on both sides of the Marmara pull-apart, are in the order of 10 mm/yr, about one half of that expected from geodetic measurements and accepted plate-tectonic models. In the southern branch of the NAF, the estimated rate of ˜4 mm/yr is only slightly higher than that given by geodetic models. Our findings have implications for both neo-tectonic reconstructions of the submerged portion of the NAF system, and fault interactions and seismic hazard estimates in the Marmara region. They suggest that, either the total Anatolia/Eurasia plate motion is more diffuse than previously reported, or geodetic data are not representative of the geological time-scale deformations. Moreover, they suggest that a significant amount of stress is accommodated along the southern strand of the NAF system, on which the last large (M ≈ 7) earthquakes dates back to 1419, 1855 and 1863 AD.
    Tectonics 01/2011; 30(6):TC6001. · 3.49 Impact Factor
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    ABSTRACT: An open problem concerning the Mw 7.4, 1999 İzmit earthquake along the North Anatolian Fault (NAF) system is the apparent conflict between estimates of strike-slip deformation based on field and remote sensing data. This is due to the fact that the main strand of the NAF west of the epicenter lies below the Sea of Marmara. Seismological evidence and models based on synthetic aperture radar interferometry suggest that coseismic and early postseismic displacement accumulated after the earthquake could have reached the western end of the İzmit Gulf and possibly the southern edge of the Çınarcık Basin, tapering off along the northern coast of the Armutlu Peninsula, more than 60 km from the epicenter. This scenario is not confirmed by onshore field observations that point toward a termination of the surface rupture around 30 km to the east. These discrepancies convey high uncertainties in the estimate of the tectonic load produced by the İzmit earthquake on the adjacent fault segment toward Istanbul. We analyzed data from different sources, including high-resolution marine geophysical surveys and two Nautile dives along the fault-controlled canyon that connects İzmit Çınarcık basins. Our observations suggest that the surface rupture of the 1999 İzmit earthquake propagated through the shallow Gulf but did not reach the deep Marmara basins. In fact, along the slope between Çınarcık and the western end of the İzmit Gulf, we do not observe fault-related ruptures affecting the seafloor but rather a series of active gas seeps and "black patches" that mark the presence of known active faults. Our findings have implications for seismic risk assessment in the highly populated region of Istanbul, both for the estimate of tectonic load transferred to the next fault segments and the location of the next earthquake.
    Tectonics 01/2011; 30(1):TC1010. · 3.49 Impact Factor
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    ABSTRACT: Aerial digital photogrammetry and laser scanning (lidar) and marine multibeam bathymetry can play a fundamental role in the generation of digital terrain models (DTMs) of land and submarine areas, respectively. Integrating these survey techniques is crucial for providing accurate and homogeneous DTMs along narrow coastal zones that often cannot be adequately surveyed owing to logistical limitations on collecting bathymetric data in shallow water. In this project, three aerial photogrammetric surveys, two multibeam bathymetric surveys and a lidar survey were analysed and integrated in the same reference system in order to generate the first 3D high resolution “digital terrain and marine model” (DTMM) of the volcanic island of Panarea (Aeolian Islands, Italy). This is a volcanically active area that underwent a submarine gas eruption in November 2002, and produced impacts on the environment as well as potential hazards for the local population. The DTMM shows the morphological features of this volcanic area with an average grid resolution of 1 m and a maximum elevation error of 1 m. This model will significantly improve geophysical and geomorphological studies of this volcanic island and assist in reducing future hazards.RésuméLa photogrammétrie numérique aérienne, le laser aéroportéà balayage et la bathymétrie multifaisceaux jouent un rôle fondamental dans la production de modèles numériques de terrain (MNT) de zones émergées et sous-marines. L’intégration de ces techniques de restitution fournit des modèles numériques de terrain précis et homogènes sur d’étroites bandes côtières qui sont souvent difficiles à cartographier en raison des difficultés pratiques liées à l’obtention de données bathymétriques en eaux peu profondes. Dans cet article, trois levés photogrammétriques aériens, deux levés bathymétriques multifaisceaux et un levé lidar sont analysés et intégrés dans le même système de référence afin de produire le premier modèle numérique terrestre et marin de l’île volcanique de Panarea (Iles Éoliennes, Italie). Il s’agit d’une zone volcanique active où une éruption gazeuse sous-marine s’est produite en novembre 2002, entraînant des impacts environnementaux ainsi que des menaces potentielles pour la population locale. Ce modèle montre les caractéristiques morphologiques de cette zone volcanique avec un pas d’échantillonnage moyen de 1 m et une erreur altimétrique maximale de 1 m. Ce modèle permettra d’améliorer de manière significative les études géophysiques et géomorphologiques de cette île volcanique et contribuera à la réduction des risques futurs.ZusammenfassungDigitale Luftbildphotogrammetrie, flugzeuggestütztes Laserscanning und Fächerlote zur Meerestiefenmessung spielen eine zentrale Rolle bei der Generierung digitaler Geländemodelle (DTM) von Land- und Meeresbodenflächen. Eine Integration dieser Vermessungstechniken trägt entscheidend zur Gewinnung genauer und homogener Digitaler Geländemodelle entlang schmaler Küstenstreifen bei. Diese können oft nicht in adäquater Weise allein durch Bathymetrie im flachen Wasser wegen logistischer Begrenzungen erfasst werden. Dieser Beitrag stellt drei Bildflüge, zwei Tiefenmessungen mit Fächerloten und einen Laserscanning Datensatz aus einer Befliegung vor, die analysiert und in das gleiche Referenzsystem integriert wurden, um das erste hochauflösende Digitale Gelände- und Marine Modell (DTMM) der Vulkaninsel Panarea (Äolische Inseln, Italien) zu erstellen. Dies ist ein vulkanisch aktives Gebiet, das im November 2002 einer Unterwassergaseruption ausgesetzt war, die die Umwelt beeinflusste und die lokale Bevölkerung potentiellen Gefahren aussetzte. Das DTMM zeigt morphologische Merkmale des vulkanischen Gebietes mit einer mittleren Gitterweite von 1 m und einem maximalen Höhenfehler von 1 m. Mit diesem Modell können geophysikalische und geomorphologische Studien dieser Vulkaninsel deutlich verbessert, und zukünftige Gefährdungen reduziert werden.ResumenLa fotogrametría aérea digital, el escáner laser aéreo y la batimetría multihaz juegan un papel fundamental en la producción de modelos digitales del terreno de áreas subaéreas y submarinas. La integración de estas técnicas de obtención de datos es crucial para producir modelos homogéneos y exactos de bandas estrechas a lo largo de la costa, y que a menudo no pueden ser exploradas por las limitaciones logísticas para la toma de datos batimétricos en aguas someras. En este artículo se analizan tres vuelos fotogramétricos, dos barridos batimétricos multihaz y un vuelo lidar que se integran en un mismo sistema de referencia para calcular el primer modelo digital tridimensional de alta resolución del terreno y marino (DTMM) de la isla volcánica de Panarea (Islas Eolias, Italia). Esta es un área volcánica activa que sufrió una erupción submarina de gas en noviembre de 2002 que impactó el medio ambiente y que representa un peligro para la población local. El modelo complejo obtenido muestra los rasgos morfológicos de esta área volcánica con una resolución espacial media de 1 m y un error medio de elevación de 1 m. Este modelo permitirá mejorar significativamente los estudios geofísicos y geomorfológicos de esta isla volcánica y ayudará a la reducción del peligro.
    The Photogrammetric Record 11/2010; 25(132):382 - 401. · 1.44 Impact Factor
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    ABSTRACT: Trasimeno, a ~10km diameter, shallow (
    Tectonophysics 01/2010; 492(1-4):164-174. · 2.68 Impact Factor