http://hdl.handle.net/2122/261 Ricerca nel canale cerca http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/6068 Titolo: Volcanological and structural evolution of the Ischia resurgent caldera (Italy) over the past 10 k.y.<br/><br/>Autori: De Vita, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Sansivero, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Orsi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Marotta, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Piochi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia<br/><br/>Curatori: Groppelli, G.; Viereck-Goette, L.<br/><br/>Abstract: Volcanic activity on the island of Ischia in the past 10 k.y. has included botheffusive and explosive eruptions, mainly in the eastern sector of the island. Vent location,eruption dynamics, transport mechanisms, and depositional processes have beenreconstructed for each recognized lithostratigraphic unit. Periods of quiescence havealternated with periods of very intense volcanism, mainly concentrated at ca. 5.5 kaand over the past 2.9 k.y. Volcanism has not been continuous, but it has been stronglyinfl uenced by the mechanism of a resurgence phenomenon that has affected theisland since ca. 33 ka. Therefore, it has been hypothesized that magma intrusion anduplift events have occurred intermittently. In the past 5.5 k.y., volcanic activity hasbeen invariably accompanied by the emplacement of slope instability–related deposits,illustrating that the slope instability was also induced by reactivation of verticalmovements, likely related to resurgence. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/2122/6036 Titolo: Predicting the impact of lava flows at Mount Etna, Italy<br/><br/>Autori: Crisci, G.; Department of Earth Sciences, University of Calabria, 87036 Rende, Italy; Avolio, M. V.; Department of Mathematics, University of Calabria, 87036 Rende, Italy; Behncke, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; D'Ambrosio, D.; Department of Mathematics, University of Calabria, 87036 Rende, Italy; Di Gregorio, S.; Department of Mathematics, University of Calabria, 87036 Rende, Italy; Lupiano, V.; Department of Earth Sciences, University of Calabria, 87036 Rende, Italy; Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Romgo, R.; Department of Earth Sciences, University of Calabria, 87036 Rende, Italy; Spataro, W.; High Performance Computing Centre, University of Calabria, 87036 Rende, Italy<br/><br/>Abstract: Forecasting the time, nature, and impact of future eruptions is difficult at volcanoessuch as Mount Etna, in Italy, where eruptions occur from the summit and on the flanks,affecting areas distant from each other. Nonetheless, the identification and quantificationof areas at risk from new eruptions are fundamental for mitigating potential humancasualties and material damage. Here, we present new results from the application of amethodology to define flexible high‐resolution lava invasion susceptibility maps based ona reliable computational model for simulating lava flows at Etna and on a validationprocedure for assessing the correctness of susceptibility mapping in the study area.Furthermore, specific scenarios can be extracted at any time from the simulation database,for land use and civil defense planning in the long term, to quantify, in real time, theimpact of an imminent eruption, and to assess the efficiency of protective measures. Wed, 28 Apr 2010 00:00:00 GMT http://hdl.handle.net/2122/6035 Titolo: Insights into fluid circulation across the Pernicana Fault (Mt. Etna, Italy) and implications for flank instability<br/><br/>Autori: Siniscalchi, A.; Dipartimento di Geologia e Geofisica, Università degli Studi di Bari, via Orabona, 4-70125, Bari-Italy; Tripaldi, S.; Dipartimento di Geologia e Geofisica, Università degli Studi di Bari, via Orabona, 4-70125, Bari-Italy; Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Giammanco, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Piscitelli, S.; Istituto di Metodologie per l' Analisi Ambientale, CNR, Tito (PZ), Italy; Balasco, M.; Istituto di Metodologie per l' Analisi Ambientale, CNR, Tito (PZ), Italy; Behncke, B.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Magri, C.; Dipartimento di Geologia e Geofisica, Università degli Studi di Bari, via Orabona, 4-70125, Bari-Italy; Naudet, V.; Université Bordeaux 1, Geosciences Hydrosciences Material and Constructions, GHYMAC-EA 4134, Talence, F-33405, France; Rizzo, E.; Istituto di Metodologie per l' Analisi Ambientale, CNR, Tito (PZ), Italy<br/><br/>Abstract: We conducted geophysical–geochemical measurements on a ∼2 kmN–S profile cutting across the PernicanaFault, one of the most active tectonic features on the NE flank of Mt. Etna. The profile passes from theunstable E flank of the volcano (to the south) to the stable N flank and significant fluctuations in electricalresistivity, self-potential, and soil gas emissions (CO2, Rn and Th) are found. The detailed multidisciplinaryanalysis reveals a complex interplay between the structural setting, uprising hydrothermal fluids, meteoricfluids percolating downwards, ground permeability, and surface topography. In particular, the recoveredfluid circulation model highlights that the southern sector is heavily fractured and faulted, allowing theformation of convective hydrothermal cells. Although the existence of a hydrothermal system in a volcanicarea does not surprise, these results have great implications in terms of flank dynamics at Mt. Etna. Indeed,the hydrothermal activity, interacting with the Pernicana Fault activity, could enhance the flank instability.Our approach should be further extended along the full extent of the boundary between the stable andunstable sectors of Etna for a better evaluation of the geohazard in this active tectonic area. Thu, 01 Apr 2010 00:00:00 GMT http://hdl.handle.net/2122/5872 Titolo: Flank instability at Mount Etna: testing the sensitivity of forward models to the internal structure<br/><br/>Autori: Cianetti, Spina; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Giunchi, Carlo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia<br/><br/>Abstract: The deformation recorded at Mount Etna during the last 15 years clearly shows that there is an interplay between activity of magmatic sources and instability of the SE sector. In particular, the anomalous sliding of the SE flank can be triggered by summit or flank eruptions (e.g., 2002), but it is also observed during quiescent loading phases (e.g., 1993-1997). This deformation is usually modeled by sub-horizontal dislocation surfaces (embedded in an elastic half space) whose parameters are determined fitting the observed surface deformation. The purpose of this paper is to investigate whether models forced by a simple isotropic expansion source but taking into account the internal structure of Mount Etna are capable to focus a significant amount of horizontal deformation in the eastern flank. We perform computations based on the finite element method along a 2D cross section. The deformation models include both topography and a synthetic reconstruction of the internal layering constrained by geology, seismic tomography and experimental measurements of Etnean rocks. We study the sensitivity of the predicted surface displacement to variations of internal layers rheology and/or mechanical parameters. Our first results suggest that significant contributions to increase the deformation in the SE sector are due to plastic rheology of the clay layers and to asymmetrical distribution of elastic parameters related to the high velocity body underneath Mount Etna imaged by seismic tomography. Mon, 14 Dec 2009 00:00:00 GMT http://hdl.handle.net/2122/5866 Titolo: MODELING OF HYDROTHERMAL FLUID CIRCULATION AS A TOOL FOR VOLCANIC HAZARD ASSESSMENT<br/><br/>Autori: Rinaldi, A. P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Vandemeulebrouck, LGIT, Université de Savoie, Le Bourget du Lac Cedex; Todesco, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia<br/><br/>Abstract: Monitoring of geophysical and geochemical observ¬ables at the surface plays a main role in the under¬standing of—and the hazard evaluation of— active volcanoes. Measurable changes in these parameters should occur when a volcano approches eruptive con¬ditions. Hydrothermal activity is commonly studied as an efficient carrier of signals from the magmatic system. As the magmatic system evolves, the amount, temperature, and composition of magmatic fluids that feed the hydrothermal system change, in turn affecting the parameters that are monitored at the surface. Modeling of hydrothermal circulation, as shown in the past, may cause measurable gravity changes and ground deformation. In this work, we extend our previous studies and increase the number of observable parameters to include gas temperature, the rate of diffuse degassing, the extent of the degassing area, and electrical conductivity. The possibility of nonmagmatic disturbance needs to be carefully addressed to ensure a proper estimate of volcanic hazard. Tue, 01 Sep 2009 00:00:00 GMT http://hdl.handle.net/2122/5860 Titolo: Hydrothermal instability and ground displacement at the Campi Flegrei caldera<br/><br/>Autori: Rinaldi, A. P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Todesco, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Bonafede, M.; University of Bologna<br/><br/>Abstract: Ground deformation is commonly observed at active volcanoes, where it represents a reliable sign of unrest and a potential precursor of eruptive activity. The source of deformation, however, is not always unequivocally constrained. Magma ascent and differentiation are generally involved, buthydrothermal fluids may play a role, due to thermal expansion and pore pressure acting on rocks. The identification of mechanisms driving ground displacement bears important consequences for hazard evaluation. The aim of this work is to evaluate mechanical effects associated with pressurization and heating of hydrothermal fluids. We first simulate the heat and fluid flow driven by the arrival of magmatic fluids from greater depth. Then, we calcu-late the rock deformation arising from simulated pressure and temperaturechanges within a shallow hydrothermal system. We employ a mathematicalmodel, based on the linear theory of thermo-poro-elasticity and on a systemof distributed equivalent forces. Results show that stronger degassing of amagmatic source may cause several centimeters of uplift. Fri, 01 Jan 2010 00:00:00 GMT http://hdl.handle.net/2122/5834 Titolo: Active degassing structures of Stromboli and variations in diffuse CO2 output related to the volcanic activity<br/><br/>Autori: Carapezza, M. L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Ricci, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Ranaldi, M.; Dipartimento di Scienze Geologiche, Università Roma Tre, Largo S. Leonardo Murialdo 1, Rome, Italy; Tarchini, L.; Dipartimento di Scienze Geologiche, Università Roma Tre, Largo S. Leonardo Murialdo 1, Rome, Italy<br/><br/>Abstract: The main CO2 diffuse degassing structures (DDS) of Stromboli were identified through extensive CO2 soil fluxinvestigations, with 3600 measurements by an accumulation chamber. These DDS extend from the nearbycrater area of Pizzo sopra la Fossa (Pizzo) to the coastal area of Pizzillo and are all associated with NE–SWdeep fractures, corresponding to the main volcano-tectonic axis of the island, some of which produced flankeruptions in prehistoric times. In each of the four main DDS, a target area was defined covering the zone withthe highest CO2 soil flux, where periodic CO2 flux surveys were carried out. The highest CO2 release wasobserved during the 2007 eruption and high flux values were recorded at both Pizzo and Pizzillo also inmoments of high prolonged Strombolian activity (high number of daily explosions observed from the cratersand/or high frequency of VLP seismic events). In order to better investigate the rate of diffuse CO2 degassingin relation to volcanic activity, an automatic station hourly measuring CO2 soil flux and environmentalparameters (atmospheric T, P and humidity, soil moisture and T, wind speed and direction) was installed inMarch 2007 at Nel Cannestrà and Rina Grande DDS. Unusual positive correlations were found at NelCannestrà between gas flux and SE wind speed and at Rina Grande between gas flux and soil moisture, whichare explained by the local conditions, which favour respectively a Venturi effect and the increase in gas fluxtoward the station during rains. Ten months of continuous recording confirmed the strong influence ofenvironmental conditions on the CO2 soil flux, but statistical data processing made it possible to recognizeclear positive anomalies expressing high rates of deep magmatic CO2 degassing. Comparison with seismicdata indicates that high CO2 fluxes are apparently correlated with increases in volcanic activity, such ashigher explosion frequency and VLP amplitude. Particularly promising is the temporal coincidence of highestrecorded flux anomaly with a major explosion that occurred during the observation period. Data confirm thatthe two continuously monitored DDS are preferentially deep degassing sites, where anomalous increases ofCO2 release could represent a geochemical precursor for either high energy explosions from the craters or theopening of flank eruptive fissures that might threaten the village of Stromboli. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2122/5833 Titolo: Large-eddy simulation of pyroclastic density currents<br/><br/>Autori: Esposti Ongaro, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Barsotti, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Neri, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Salvetti, M. V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia<br/><br/>Abstract: We investigate the dynamics of turbulent pyroclastic density currents (PDCs) by adopting a 3D, Eulerian-Eulerian multiphase flow model, in which solid particles are treated as a continuum and the grain-size distribution is simplified by assuming two particulate phases. The turbulent sub-grid stress of the gas phase is modelled within the framework of Large-Eddy Simulation (LES) by means of a eddy-viscosity model together with a wall closure. Despite the significant numerical diffusion associated to the upwind method adopted for the Finite-Volume discretization, numerical simulations demonstrate the need of adopting a Sub-Grid Scale (SGS) model, while revealing the complex interplay between the grid and the SGS filter sizes. We also analyse the relationship between the averaged flow dynamic pressure and the action exerted by the PDC on a cubic obstacle, to evaluate the impact of a PDC on a building. Numerical results suggest that the average flow dynamic pressure can be used as a proxy for the force per unit surface acting on the building envelope (Fig. 5), even for such steeply stratified flows. However, it is not possible to express such roportionality as a constant coefficient such as the drag coefficient in a steady-state current. The present results indeed indicate that the large epistemic and aleatory uncertainty on initial and boundary conditions has an impact on the numerical redictions which is comparable to that of grid resolution. Thu, 01 Jan 2009 00:00:00 GMT http://hdl.handle.net/2122/5819 Titolo: The magmatic engine of unrest episodes at Campi Flegrei caldera (southern Italy)<br/><br/>Autori: Moretti, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Berrino, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Arienzo, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Chiodini, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Civetta, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Orsi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia<br/><br/>Abstract: Volcanic calderas are affected by unrest episodes usually dominated byhybrid magmatic-hydrothermal system dynamics, but which can evolve tovariable intensity eruptions, up to Plinian. Campi Flegrei caldera... Thu, 01 Oct 2009 00:00:00 GMT http://hdl.handle.net/2122/5775 Titolo: A note on maar eruption energetics: current models and their application<br/><br/>Autori: 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<br/><br/>Abstract: Hydromagmatic eruptions convert thermal intomechanical energy via the expansion of ground- and/orsurface-water. Several models address the energetics ofthese eruptions based on different physical-volcanologicalapproaches. Here we test different models with two casestudies in the Colli Albani Volcanic District (central Italy):the monogenetic Prata Porci and the polygenetic Albanomaars. Test results are mutually consistent, and showcumulative mechanical energy releases on the order of1015–1017J for single maars. The fraction of thermal energyturned into mechanical ranges from 0.45 (as calculated fromthe theoretical maximum mechanical energy), through 0.1(calculated from country rock fragmentation, crater formationand ballistic ejection), to 0.03 (derived from magmafragmentation by thermohydraulic explosions). It appearsthat the energy released during the most intense hydromagmaticevents may account for a dominant fraction of thetotal mechanical energy released during the whole maareruptive histories. Finally, we consider the role of magmaticexplosive activity intervening during maar eruptions incausing departures from predictions of the models evaluated. Fri, 01 Jan 2010 00:00:00 GMT