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Ventura, Guido
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Preferred name
Ventura, Guido
Email
guido.ventura@ingv.it
Staff
staff
ORCID
Scopus Author ID
7101605885
Researcher ID
A-6099-2009
146 results
Now showing 1 - 10 of 146
- PublicationOpen AccessAnalisi morfometrica integrata in ambiente GIS applicata ad aree tettonicamente attive come contributo alla valutazione dei rischi ambientali(2007)
; ; ; ; ; ;Nappi, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Alessio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Vilardo, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Bellucci Sessa, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Ventura, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; ; ; L'obiettivo di questo lavoro è quello di sperimentare e descrivere una metodologia integrata di indagine che possa essere valida per l'analisi delle deformazioni indotte sul territorio dalla tettonica e dalla morfogenesi a scala regionale e locale.266 602 - PublicationRestrictedGeomorphological map of the Somma-Vesuvius volcanic complex (Italy)(2005)
; ; ; ; ; ; ;Ventura, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Vilardo, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Bronzino, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Gabriele, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Nappi, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Terranova, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; ; ; ; The first geomorphological map of the Somma-Vesuvius active volcano is presented. This map includes the volcanic and epivolcanic landforms at a 1:10.000 scale.The map is obtained combining the available geological information with data derived from: (a) Digital Terrain Model (DTM), (b) image analysis of aerial views and interpretation of topographic maps, (c) field surveys. At Somma-Vesuvius, epivolcanic landforms concentrated in the northern and eastern sectors of the volcano. Volcanic landforms characterize the caldera area, the western and the southern sectors, where the most recent (1631-1944) activity occurred.414 249 - PublicationOpen AccessVein networks in hydrothermal systems provide constraints for the monitoring of active volcanoes(2017)
; ; ; ; ; ; ; Vein networks affect the hydrothermal systems of many volcanoes, and variations in their arrangement may precede hydrothermal and volcanic eruptions. However, the long-term evolution of vein networks is often unknown because data are lacking. We analyze two gypsum-filled vein networks affecting the hydrothermal field of the active Lipari volcanic Island (Italy) to reconstruct the dynamics of the hydrothermal processes. The older network (E1) consists of sub-vertical, N-S striking veins; the younger network (E2) consists of veins without a preferred strike and dip. E2 veins have larger aperture/length, fracture density, dilatancy, and finite extension than E1. The fluid overpressure of E2 is larger than that of E1 veins, whereas the hydraulic conductance is lower. The larger number of fracture intersections in E2 slows down the fluid movement, and favors fluid interference effects and pressurization. Depths of the E1 and E2 hydrothermal sources are 0.8 km and 4.6 km, respectively. The decrease in the fluid flux, depth of the hydrothermal source, and the pressurization increase in E2 are likely associated to a magma reservoir. The decrease of fluid discharge in hydrothermal fields may reflect pressurization at depth potentially preceding hydrothermal explosions. This has significant implications for the longterm monitoring strategy of volcanoes.464 58 - PublicationOpen AccessFluid Vents, Flank Instability, and Seafloor Processes along the Submarine Slopes of the Somma-Vesuvius Volcano, Eastern Tyrrhenian MarginWe report the geomorphological features of the continental shelf of the Gulf of Naples along the submarine slopes of the Somma-Vesuvius volcanic complex. This area is characterized by seafloor morphologies that are related to mantle degassing. Significant phenomena associated with this process occur. Doming of the seafloor has been detected in the area of Banco della Montagna, whereas a hole-like morphology has formed at Bocca dei Pescatori, likely as a result of a phreatic explosion. Outcropping or partially submerged volcanic bodies are also present as well as two main debris avalanche deposits arising from the main Somma-Vesuvius edifice. A large area characterized by an overall concave external profile and a global sediment wave morphology covers most of the southwestern area of the volcano.
150 58 - PublicationRestrictedThe effect of particle size on the rheology of liquid-solid mixtures with application to lava flows: Results from analogue experiments(2013-08-02)
; ; ; ;Del Gaudio, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Ventura, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Taddeucci, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; We investigate the effect of crystal size on the rheology of basaltic magmas by means of a rheometer and suspensions of silicon oil with natural magmatic crystals of variable size (from 63 to 0.5 mm) and volume fraction fi (from 0.03 to 0.6). At constant fi, finer suspensions display higher viscosities than coarser ones. Shear thinning (flow index n < 1) occurs at fi > 0.1–0.2 and is more pronounced (stronger departure from the Newtonian behavior) in finer suspensions. Maximum packing and average crystal size displays a nonlinear, positive correlation, while yield stress develops at fi > 0.2–0.3 irrespective of the crystal size. We incorporate our results into physical models for flow of lava and show that, with respect to lava flows containing coarser crystals, those with smaller crystals are expected to: 1) flow at lower velocity, 2) have a lower velocity gradient, and 3) be more prone to develop a region of plug flow. Our experimental results explain the observation that phenocryst-bearing and microlite-bearing lavas at Etna volcano (Italy) show smooth pahoehoe and rough aa’ surfaces, respectively.297 30 - PublicationRestrictedSeismic and Geodetic Evidences of a Hydrothermal Source in the Md 4.0, 2017, Ischia Earthquake (Italy)(2019-05-02)
; ; ; ; ; ; ; ; ; ; ; ; ; Seismic events characterize active hydrothermal and volcanic areas and may be due to magma/fluid migration, hydrothermal pressurization, gravitational instability, and local tectonics. On 21 August 2017, an Md 4.0 earthquake occurred at Ischia volcanic island (Italy), within an active hydrothermal system. We analyze seismic, Global Positioning System, and interferometric synthetic aperture radar data to shed light on the source mechanism of such an event. The low‐frequency content (2 Hz), the low stress drop (0.01 MPa), and a low S/P spectral ratio suggest the involvement offluids in the source mechanism. The focal mechanism suggests a mixed shear‐tensile (opening) rupture with the P first arrivals showing up movements in the nearest stations. Geodetic data describe an E‐W elongated area of coseismic subsidence overlapping a WSW‐ENE fault bounding the hydrothermal reservoir at depth. The modeled deformation field is consistent with a two‐source model consisting of a WSW‐ESE striking, north dipping normal fault, and a closing subhorizontal crack. This closure immediately followed an initial opening related to a fluid pressurization event responsible for the earthquake. We show that moderate magnitude earthquakes in active hydrothermal areas may be associated with the pressurization/depressurization cycles of a hydrothermal reservoir due to self‐sealing processes and not to the arrival of new fluids from depth. Other events like that recorded at Ischia, which have affected the island in historical times, are not necessarily associated with ‘volcanic unrest’ episodes and imply the occurrence of fault‐valve mechanisms. Therefore, the dynamics of hydrothermal systems must be taken into account in the seismic hazard evaluation.467 7 - PublicationOpen AccessSeismic Sensors Probe Lipari’s Underground Plumbing(2019)
; ; ; ; ; ; ; ;; ; ; Just north of the island of Sicily, near the toe of Italy’s “boot,” a chain of volcanic islands traces a delicate arc in the Mediterranean Sea. This chain, the Aeolian Islands, popular tourist resorts in proximity to some of Earth’s most active and well-known volcanoes, including Etna and Stromboli. Lipari, the largest of these islands, lies of the island of Vulcano, for which these eruptive features are named. Lipari is less well characterized than some of the other nearby volcanoes, but one research group setting out to change this. This is the first time that a dense seismic array has been deployed to investigate a hydrothermal system in the volcanically active Aeolian Islands. Lipari is located ~80 kilometers north of the well-monitored Etna volcano. The island’s hydrothermal system, in which magma heats the water underground, is not to eruptive centers, but, rather, is connected to the regional fault system that delimits the western boundary of the active Ionian subduction zone. Lipari holds a unique place in our understanding of the tectonic evolution and hydrothermal activity of volcanoes emplaced in subduction zones (https://eos.org/projectupdates/ understanding-volcanic-eruptions-where-plates-meet). Within the framework of the ring-shaped Aeolian arc, the unexpected NNW–SSE alignment of Lipari andbeen related to a major regional discontinuity, the Tindari-Letojanni (https://www.researchgate.net/publication/311738886_Structural_architecture_and_active_deformation_pattern_in_the_northern_sector_of_the_Aeolian-Tindari- Letojanni_fault_system_SE_Tyrrhenian_Sea-NE_Sicily_from_integrated_analysis_of_field_marine_geophys) subduction transform edge propagator (STEP (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015JB012202)) fault, a tear in a tectonic plate that allows one part of the plate to plunge downward while an adjacent remains on the surface.535 55 - PublicationOpen AccessGeochronology and Petrogenesis of Early Pleistocene Dikes in the Changbai Mountain Volcanic Field (NE China) Based on Geochemistry and Sr-Nd-Pb-Hf Isotopic Compositions(2021)
; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ;Changbai Mountains intraplate volcanism (NE China) developed above the 500 km deep stagnant portion of the Pacific slab in the last 20 Ma. The more recent activity includes a shieldforming stage (2.8–0.3Ma), the Tianchi cone construction stage (1.5–0.01Ma), and a calderaforming stage (0.2Ma-present). Detailed studies on the petrogenesis of the volcanic products between the first two stages and the possible role of geodynamics and local tectonics in controlling the volcanism, however, are lacking. Here, we present structural and whole-rock geochemical and zircon Hf isotopic data on Pleistocene dikes of the Changbai Mountains at the transition from the shield-forming to the Tianchi stage with the aim to constrain their age and the source(s) of their parental magma. The dikes represent the shallower feeding system of monogenetic cones and have a NW-SE strike, which is also the preferred strike of the major fault affecting the area and along which the Changbai Mountains monogenetic scoria cones align. The dikes have a potassic affinity and a trachybasaltic composition. Their zircon U–Pb age is 1.19–1.20Ma (Calabrian). The trachybasalts are enriched in Rb, Ba, Th, U, Nb, Ta, K, Pb, and LREE and slightly depleted in Sr, Zr, Hf, Ti, and HREE with a weak negative Eu/Eu* (δEu 0.96–0.97). Trace elements and isotopic compositions are compatiblewith anOIB-type source with an EMI signature. The calculated (87Sr/86Sr)i ( 0.705165–0.705324), (143Nd/ 144Nd)i ( 0.512552–0.512607, εNd(t) −0.58 to −1.65), and Hf model ages (TDM2) of 1768–1562 Ma suggest that the trachybasaltic dikes were contaminated by a Mesoproterozoic, relatively basic lower crust. The source of the Calabrian trachybasalts consists of asthenospheric melts modified by a subcontinental lithospheric mantle. These melts upwell from depth and stop at the crust-mantle interface where underplating processes favor the assimilation of ancient lower crust material. During the ascent to the surface along deep-seated crustal discontinuities, these magmas weakly differentiate.93 41 - PublicationRestrictedA note on maar eruption energetics: current models and their application(2010)
; ; ; ; ; ;Taddeucci, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Sottili, G.; University La Sapienza, Italy ;Palladino, D.; University La Sapienza, Italy ;Ventura, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Scarlato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ; Hydromagmatic eruptions convert thermal into mechanical energy via the expansion of ground- and/or surface-water. Several models address the energetics of these eruptions based on different physical-volcanological approaches. Here we test different models with two case studies in the Colli Albani Volcanic District (central Italy): the monogenetic Prata Porci and the polygenetic Albano maars. Test results are mutually consistent, and show cumulative mechanical energy releases on the order of 1015–1017J for single maars. The fraction of thermal energy turned into mechanical ranges from 0.45 (as calculated from the theoretical maximum mechanical energy), through 0.1 (calculated from country rock fragmentation, crater formation and ballistic ejection), to 0.03 (derived from magma fragmentation by thermohydraulic explosions). It appears that the energy released during the most intense hydromagmatic events may account for a dominant fraction of the total mechanical energy released during the whole maar eruptive histories. Finally, we consider the role of magmatic explosive activity intervening during maar eruptions in causing departures from predictions of the models evaluated.198 25 - PublicationOpen AccessGeomorphological map of the 1944 Vesuvius lava flow (Italy).(2008)
; ; ;Vilardo, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Ventura, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; The map of the 1944 lava flow shows the geomorphological characteristics of a sector of the Vesuvius volcano (Italy) covered by the products emitted during the last effusive phase. The map has been produced based on the analysis and interpretation of (a) thematic maps (slope, aspect, relative relief) derived from a high resolution (0.33 m pixel) Digital Terrain Model (DTM) obtained by a Airborne Laser Scanning (ASL) survey, and (b) a 1 m pixel digital colour orthophoto. Different flow structures and morphologies have been recognized. The analytical approach proposed here can be used to characterize the smaller scale topographic/geomorphological features of volcanoes and gives constraints on the mechanism of emplacement and modelling strategies of lava flows.192 309