http://hdl.handle.net/2122/259 Fri, 24 May 2013 06:17:40 GMT 2013-05-24T06:17:40Z http://hdl.handle.net/2122/8662 Title: The Volcano-Seismic Clock of the South American Pacific Margin - A Possible First Link Between Natural Disasters Prevention and Expanding Earth Authors: Scalera, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Editors: Scalera, Giancarlo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: A volcano-seismic correlation was for a long time suspected to occur on the Pacific margin of South America. Scalera (2008) using the data available in 2006 in the Smithsonian Institution Catalogue of the volcanic eruptions, has revealed evidence that earthquakes happened into the South-American Wadati-Benio zone – with magnitude greater than 8.4 –are associated to an enhanced rate of volcanic eruptions, but has been impossible to determine the causal chain between the two phenomena. After 2006, the effort of the Smithsonian Institution to improve our knowledge of this region has resulted in a greatly increased completeness of the catalogue, adding the new eruptions for the 2000- 2010 interval, but also an additional 50% of new entries in the list of the Andean volcanoes. The occurrence of the Chilean earthquake of Maule – 27 February 2010 (M=8.8); occurred at five decades from the 1960 quake – has been the occasion to rework all the data searching for additional clues able to indicate a preferred causal direction eruptions-earthquakes or earthquakes-eruptions – or from a third more general cause (e.g. a mantle movements) to both eruptions and earthquakes. This short note discusses the three above-said hypotheses and tries to establish if these results could be useful to the aims of the Civil Protection in the programs of prevention and/or forecasting of natural disasters. Fri, 30 Nov 2012 23:00:00 GMT http://hdl.handle.net/2122/8662 2012-11-30T23:00:00Z http://hdl.handle.net/2122/8384 Title: Coeval strombolian and vulcanian-type explosive eruptions at Panarea (Aeolian Islands, Southern Italy) Authors: Cimarelli, C.; Università degli Studi di Roma Tre; De Rita, D.; Università degli Studi di Roma Tre; Dolfi, D.; Università degli Studi di Roma Tre; Procesi, M.; Università degli Studi di Roma Tre Abstract: In this paper, we document the evolution of the emergent Panarea dome in the Aeolian islands (Southern Italy), placing particular emphasis on the reconstruction of the explosive events that occurred during the final stage of its evolution. Two main pyroclastic successions exposing fall deposits with different compositions have been studied into detail: the andesitic Palisi succession and the basaltic Punta Falcone succession. The close-in-time deposition of the two successions, the dispersal area and grain-size distribution of the deposits account for their attribution to vents located in the western sector of the present island and erupting almost contemporaneously. Vents could have been aligned along NNE-trending regional fracture systems controlling the western flank of the dome and possibly its collapse. Laboratory analyses have been devoted to the characterization of the products of the two successions that have been ascribed to vulcanianand to strombolian-type eruptions respectively. The vulcanian eruption started with a vent-clearing phase that occurred by sudden decompression of a pressurized magma producing ballistic bombs and a surge blast and the development of a vulcanian plume. Vulcanian activity was almost contemporaneous to stromboliantype fall-out eruptions. The coeval occurrence of basaltic and andesitic eruptions from close vents and the presence of magmatic basaltic enclaves in the final dacitic lava lobe of the dome allow us to speculate that the intrusion of a basaltic dyke played a major role in triggering explosive eruptions. The final explosive episodes may have been caused by extensional tectonics fracturing the roof of a zoned shallow magma chamber or by the intrusion of a new basaltic magma into a more acidic and shallow reservoir. Intrusion most likely occurred through the injection of dykes along the western cliff of the present Panarea Island inducing the collapse of the western sector of the dome. Tue, 17 Jun 2008 22:00:00 GMT http://hdl.handle.net/2122/8384 2008-06-17T22:00:00Z http://hdl.handle.net/2122/6895 Title: Preliminary geochemical characterization of volcanic and geothermal fluids discharged from the Ecuadorian volcanic arc. Authors: Inguaggiato, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Hidalgo, S.; Beate, B.; Bourquin, J. Abstract: In Ecuador, magmatism results from the subduction of the Nazca Plate beneath the North Western part of South America. North of 2.5°S, the Ecuadorian Quaternary volcanic arc is characterized by about 60 volcanoes distributed along three different parallel NNE-striking chains. Many of these volcanoes are potentially active or currently in activity displaying associated geothermal fields. South of this latitude, no active arc is present in Ecuador. Few geochemical studies of the discharged fluids in this region have been attempted, mainly related to geothermal exploration. Nevertheless, a complete study of the fluids of the volcanic arc is lacking. The aim of this work is to present the first systematic geochemical characterization of discharged fluids from the entire Ecuadorian volcanic arc. In order to achieve this objective, 56 samples of thermal and cold waters, as well as 32 dissolved and 27 bubbling gases, were collected from North to South across the arc and analyzed for determination of the main geochemical parameters. A chemical study reflects the physical and chemical processes undergone by these cold and thermal waters during their circulation through the different host rocks. The chemistry of the dissolved gases, are characterized by He and CO2 contents, 2 to 3 orders of magnitude higher than the ASW values implies very active gas-water interaction processes. Moreover, both dissolved and bubbling gases isotopic signature shows a wide compositional range, with Helium ranging between 0.1 to 7.12 R/Ra and carbon ranging from -1.75 to -10.50 13C(TDIC) vs PDB standard. Such isotopic features may be related to the presence of at least two distinct end-members: mantle and crustal.. Helium, Nitrogen, Carbon, Oxygen and Deuterium isotopic signatures will help us to identify and characterize the main end-members of fluids involved in Ecuador’s continental arc-volcanism. Moreover, on the basis of the chemistry of thermal waters and associated bubbling gases the characteristics and the potential resources of the different geothermal fields are being investigated. Thu, 30 Sep 2010 22:00:00 GMT http://hdl.handle.net/2122/6895 2010-09-30T22:00:00Z http://hdl.handle.net/2122/6254 Title: Interactions between volcanism and tctonics in the western Aeolian sector, southern Tyrrhenian Sea Authors: Bortoluzzi, G.; CNR-ISMAR Bologna; Ligi, M.; CNR-ISMAR Bologna; Romagnoli, C.; Università di Bologna; Cocchi, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Casalbore, D.; Università di Bologna; Sgroi, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cuffaro, M.; Università La Sapienza Roma; Caratori Tontini, F.; GNS Science, New Zealand; D'Oriano, F.; CNR-ISMAR Bologna; Ferrante, V.; CNR-ISMAR Bologna; Remia, A.; CNR-ISMAR Bologna; Riminucci, F.; CNR-ISMAR Bologna Abstract: New high-resolution bathymetric and magnetic data from the western Aeolian sector, southern Tyrrhenian Sea, provide insights into structural and volcanic development of the area, suggesting a strong interaction between volcanism and tectonics. The analysis of these data combined with relocated earthquake distribution, focal plane solutions and strain rate evaluation indicates that the dextral strike-slip Sisifo-Alicudi shear zone is a complex and wide area of active deformation, representing the superficial expression of the deep seated lithospheric tear fault separating the subduction slab below Sicily and Calabria. Most of the observed volcanic features are aligned along a NW–SE trend, such as the Filicudi island-Alicudi North Seamount and Eolo-Enarete alignments, and are dissected by hundred-metre-high scarps along conjugate NNE–SSW trending fault systems. The magnetic field pattern matches the main trends of volcanic features. Spectral analysis and Euler deconvolution of magnetic anomalies show the existence of both deep and shallow sources. High-amplitude, high-frequency anomalies due to shallow sources are dominant close to the volcanic edifices of Alicudi and Filicudi, while the main contribution on the surrounding Eolo, Enarete, Alicudi North and Filicudi North seamounts is given by low-amplitude anomalies and/or deeper magnetic sources. This is probably related to different ages of the volcanic rocks, although hydrothermal processes may have played an important role in blanketing magnetic anomalies, in particular at Enarete and Eolo seamounts. Relative chronology of the eruptive centres and the inferred deformation pattern outline the Quaternary evolution of the western Aeolian Arc: Sisifo, Alicudi North and Filicudi North seamounts might have developed in an early stage, following the Late Pliocene–Early Pleistocene SE-ward migration of arc-related volcanism due to the Ionian subduction hinge retreat; Eolo, Enarete and Filicudi represent later manifestations that led volcanoes to develop duringMid-Late Pleistocene, when the stress regime in the area changed, due to the SSE-ward propagation of the subduction slab tear fault and the consequent reorientation and decrease of trench migration velocity. Finally, volcanic activity occurred in a very short time span at Alicudi, where an almost conical volcanic edifice emerged, suggesting negligible interactions with regional fault systems. Thu, 31 Dec 2009 23:00:00 GMT http://hdl.handle.net/2122/6254 2009-12-31T23:00:00Z http://hdl.handle.net/2122/6235 Title: A buried volcano in the Calabrian Arc (Italy) revealed by high‐resolution aeromagnetic data Authors: De Ritis, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Dominici, R.; Department of Earth Science, Università della Calabria, Arcavacata di Rende, Italy; Ventura, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Nicolosi, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Speranza, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; De Rosa, R.; Department of Earth Science, Università della Calabria, Arcavacata di Rende, Italy; Donato, P.; Department of Earth Science, Università della Calabria, Arcavacata di Rende, Italy; Sonnino, M.; Department of Earth Science, Università della Calabria, Arcavacata di Rende, Italy Abstract: Aeromagnetic data collected between the Aeolian volcanoes (southern Tyrrhenian Sea) and the Calabrian Arc (Italy) highlight a WNW‐ESE elongated positive magnetic anomaly centered on the Capo Vaticano morphological ridge (Tyrrhenian coast of Calabria), characterized by an apical, subcircular, flat surface. Results of forward and inverse modeling of the magnetic data show a 20 km long and 3–5 km wide magnetized body that extends from sea floor to about 3 km below sea level. The magnetic properties of this body are consistent with those of the medium to highly evolved volcanic rocks of the Aeolian Arc (i.e., dacites and rhyolites). In the Calabria mainland, widespread dacitic to rhyolitic pumices with calc‐alkaline affinity of Pleistocene age (1–0.7 Ma) are exposed. The tephra falls are related to explosive activity and show a decreasing thickness from the Capo Vaticano area southeastward. The presence of lithics indicates a provenance from a source located not far from Capo Vaticano. The combined interpretation of the magnetic and available geological data reveal that (1) the Capo Vaticano WNW‐ESE elongated positive magnetic anomaly is due to the occurrence of a WNW‐ESE elongated sill; (2) such a sill represents the remnant of the plumbing system of a Pleistocene volcano that erupted explosively producing the pumice tephra exposed in Calabria; and (3) the volcanism is consistent with the Aeolian products, in terms of age, magnetic signature, and geochemical affinity of the erupted products,. The results indicate that such volcanism developed along seismically active faults transversal to the general trend of the Aeolian Arc and Calabria block, in an area where uplift is maximized (∼4 mm/yr). Such uplift could also be responsible for fragmentation of the upper crust and formation of transversal faults along which seismic activity and volcanism occur. Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union. Thu, 31 Dec 2009 23:00:00 GMT http://hdl.handle.net/2122/6235 2009-12-31T23:00:00Z http://hdl.handle.net/2122/6234 Title: Regional magnetic and gravity anomaly correlations of the Southern Tyrrhenian Sea Authors: De Ritis, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Ventura, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Carluccio, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Von Frese, R.; School of Earth Science, Ohio State University, Columbus, OH 43210, USA Abstract: The complex magnetic and gravity anomaly fields of the Southern Tyrrhenian Sea provide a record of the complicated properties and evolution of the underlying crust. Geologic interpretation of these anomalies is hindered by the effects of anomaly superposition and source ambiguity inherent to potential field analysis. A common approach to minimizing interpretational ambiguities is to consider analyses of anomaly correlations. Spectral correlation filters are used to separate positively and negatively correlated anomaly features based on the correlation coefficient given by the cosine of the phase difference between common wavenumber components. This procedure is applied to reduced-to-pole magnetic and first vertical derivative gravity anomalies for mapping correlative crustal magnetization and density contrasts. Adding and subtracting the standardized outputs of the filters yield summed (SLFI) and differenced (DLFI) local favorability indices that, respectively highlight positive and negative feature correlations in the anomaly data sets. Correlative maxima mainly reflect volcanic structures, and secondarily intrusive bodies and pre- Tortonian carbonates of the Maghrebian chain and the basement rocks of the Sardinia eastern margin. Correlative minima mostly mark sediment-filled peri-Tyrrhenian structural basins related to the Pliocene extensional tectonics, and intra-slope marine depressions related to post-Pliocene and still-active compressional tectonics off Northern Sicily. Prominent inverse anomaly correlations mainly reflect crustal features around the southern margin of the Tyrrhenian Sea that include higher density, lower magnetization pelagic-to-terrigenous and flysch-type nappes of the Sicilian-Maghrebian chain, as well as lower density, higher magnetization sediments filling depressions of the chain, and syn-rift sediments of Southeastern Sardinia. Wed, 30 Jun 2010 22:00:00 GMT http://hdl.handle.net/2122/6234 2010-06-30T22:00:00Z http://hdl.handle.net/2122/5401 Title: Modelling ground deformation caused by oscillating overpressure in a dyke conduit at Soufrière Hills Volcano, Montserrat Authors: Hautmann, S.; Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ, United Kingdom; Gottsmann, J.; Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ, United Kingdom; Sparks, R. S. J.; Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ, United Kingdom; Costa, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Melnik, O.; Institute of Mechanics, Moscow State University, 1-112b Michurinsky prosp., Moscow, Russia; Voight, B.; Department of Geosciences, Penn State University, 334A Deike Building, University Park, PA 16802, USA Abstract: A dyke conduit has been shown to be a realistic model for the shallow magmatic feeder system for the dome forming eruption at Soufrière Hills Volcano, Montserrat. Here we use a three-dimensional Finite Element model to examine the ground deformation that can be expected due to the pressurization of a dyke conduit. We find that the generated deformation has a bilateral symmetry with nearly no displacement in the direction of dyke strike, and a maximal ground deformation about 1 km away from the vent in the perpendicular direction. Resultant surface deformation is mainly triggered by the upper part of the feeder system, where the dyke opens into a cylindrical conduit. We apply our deformation model to investigate tilt data collected in 1997 in order to infer the orientation of the dyke. We obtain a best-fit for a NNW–SSE trending dyke, which matches observations of the ground displacement field obtained by differential GPS and the alignment of main structural geologic features of southern Montserrat. Wed, 31 Dec 2008 23:00:00 GMT http://hdl.handle.net/2122/5401 2008-12-31T23:00:00Z http://hdl.handle.net/2122/5110 Title: Interpretation of data from the monitoring thermal camera of Stromboli volcano (Aeolian Islands, Italy) Authors: Zanon, V.; Centro de Vulcanologia e Avaliac¸ ˜ao de Riscos Geol´ogicos, Universidade dos Ac¸ores, Rua M˜ae de Deus, 9501-801 Ponta Delgada, Portugal; Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Pecora, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia Abstract: Twenty eruptive events from the Northeast Crater of Stromboli volcano recorded by a thermal monitoring camera in early 2004 were analysed in order to understand the eruptive dynamics. Selected eventswere chosen to be typical of explosions that characterize the steady activity of Stromboli in terms of jet height and duration. Most of the explosions consisted of clast-rich single bursts, originating from the same vent inside the Northeast Crater. Conspicuous ash emission was scarce. Eruptions were preceded by the flashing of a perturbation wave characterized by low temperatures and an average propagation velocity of about 35–100 m s−1. This perturbation was thought to be caused by the bursting of the gas slug at the bottom of the crater and is interpreted as an air wave. This was immediately followed by the expansion of a jet of ‘hot’ gas and particles, at a velocity of 35–75 m s−1. Ejecta coarser than 138 cm appeared ∼1.6–2 s after the onset of the explosion, moving at a variable velocity (30–60 m s−1). Eruptive events were either vertical or inclined 7–13◦ towards the NNW. This inclination is thought to be a consequence either of the morphology of the conduit, following modest rock falls that partially obstructed the uppermost part of the crater, or of the displacement of the internal conduit due to the explosive activity of the volcano. The instability of the summit area is a further possible cause of the deformation of the conduit. Tue, 30 Jun 2009 22:00:00 GMT http://hdl.handle.net/2122/5110 2009-06-30T22:00:00Z http://hdl.handle.net/2122/5040 Title: Structural features of the 2007 Stromboli eruption Authors: Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Lanzafame, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia Abstract: On 27 February 2007, two NE–SW and NNW–SSE dike-fed effusive vents opened to the North (at 650 and 400 m above sea level, asl) of the summit craters at Stromboli, forming a fissure parallel to the inner walls of the Sciara del Fuoco (SdF) sector collapse depression. The formation of these vents was soon followed by rapid subsidence of the summit crater area. This partly obstructed the central conduit, temporarily choking the fissure and increasing the deformation of the upper part of SdF. The reactivation of the NNW–SSE vent and the opening of a new vent located at 500 m asl, fed by a second dike, released the internal pressure and surface deformation ceased. The eruption then continued again from the 400 m vent, after a summit explosion on 15 March, until ending in early April after a progressive decrease of magma output. Repeated NE–SW dike intrusions have occurred in recent years, close to the upper SE limit of the SdF. In that zone, named Bastimento, the eruptive fractures traced the discontinuities that borders the SdF, increasing the risk of triggering new sector collapse. Whereas the NE–SW trending structures lie along the regional volcanostructural trend of the Aeolian arc through Stromboli, the NNW–SSE vents are oblique to this trend and may be controlled by the anomalous stress field within the unstable flank of the SdF. Another fundamental aspect of the 2007 eruption is the collapse of the central conduit, due to the rapid and deep magma drainage linked to the opening of the 400 m vent. The intrusion of dikes and development of flank vents during the 2007 eruption could possibly have triggered catastrophic landslides and related tsunami or eruptive paroxysms, but the opening of new effusive vents released the internal pressures, diminishing the hazard. Sat, 09 May 2009 22:00:00 GMT http://hdl.handle.net/2122/5040 2009-05-09T22:00:00Z http://hdl.handle.net/2122/5038 Title: Structural features of Panarea volcano in the frame of the Aeolian Arc (Italy): Implications for the 2002–2003 unrest Authors: Acocella, V.; Dip. Sc. Geologiche Roma Tre. L.S.L. Murialdo 1, 00146 Roma, Italy; Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Walter, T. R.; Deutsches GeoForschungsZentrum (GFZ) Potsdam, Dept. Physics of the Earth, Telegrafenberg, 14473 Potsdam, Germany Abstract: Panarea, characterized by gas unrest in 2002–2003, is the volcanic island with the least constrained structure in the eastern-central Aeolian Arc (Italy). Based on structural measurements, we define here its deformation pattern relative to the Arc. The main deformations are subvertical extension fractures (63% of data), normal faults (25%) and dikes (12%). The mean orientation of the extension fractures and faults is ∼N38◦E, with a mean opening direction of N135◦ ±8◦, implying extension with a moderate component of dextral shear. These data, matched with those available for Stromboli volcano (pure opening) and Vulcano, Lipari and Salina volcanoes (predominant dextralmotions) along the eastern-central Arc, suggest a progressivewestward rotation of the extension direction and an increase in the dextral shear. The dextral shear turns into compression in the western arc. The recent unrest at Panarea, coeval to that of nearby Stromboli, may also be explained by the structural context, as both volcanoes lie along the portion of the Arc subject to extension. Thu, 30 Apr 2009 22:00:00 GMT http://hdl.handle.net/2122/5038 2009-04-30T22:00:00Z