http://hdl.handle.net/2122/267 Ricerca nel canale cerca http://www.earth-prints.org/simple-search http://hdl.handle.net/2122/6066 Titolo: Carbon dioxide diffuse emission from the soil: ten years of observations at Vesuvio and Campi Flegrei (Pozzuoli), and linkages with volcanic activity<br/><br/>Autori: Granieri, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Avino, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Chiodini, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia<br/><br/>Abstract: Carbon dioxide flux from the soil is regularlymonitored in selected areas of Vesuvio and Solfatara(Campi Flegrei, Pozzuoli) with the twofold aim of i)monitoring spatial and temporal variations of the degassingprocess and ii) investigating if the surface phenomena couldprovide information about the processes occurring at depth.At present, the surveyed areas include 15 fixed pointsaround the rim of Vesuvio and 71 fixed points in the floorof Solfatara crater. Soil CO2 flux has been measured since1998, at least once a month, in both areas. In addition, twoautomatic permanent stations, located at Vesuvio andSolfatara, measure the CO2 flux and some environmentalparameters that can potentially influence the CO2 diffusedegassing. Series acquired by continuous stations arecharacterized by an annual periodicity that is related tothe typical periodicities of some meteorological parameters.Conversely, series of CO2 flux data arising from periodicmeasurements over the arrays of Vesuvio and Solfatara areless dependent on external factors such as meteorologicalparameters, local soil properties (porosity, hydraulic conductivity)and topographic effects (high or low ground).Therefore we argue that the long-term trend of this signalcontains the “best” possible representation of the endogenoussignal related to the upflow of deep hydrothermalfluids. http://hdl.handle.net/2122/6062 Titolo: The source of infrasound associated with long-period events at Mount<br/><br/>Autori: Matoza, R. S.; Laboratory for Atmospheric Acoustics, Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California; Garcés, M. A.; Infrasound Laboratory, Hawai’i Institute of Geophysics andPlanetology, University of Hawai’i at Manoa; Chouet, B. A.; U.S. Geological Survey, Menlo Park, California; D' Auria, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Hedlin, M. A. H.; Laboratory for Atmospheric Acoustics, Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California; De Groot-Hedlin, E.; Laboratory for Atmospheric Acoustics, Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California; Waite, G. P.; U.S. Geological Survey, Menlo Park, California<br/><br/>Abstract: During the early stages of the 2004–2008 Mount St. Helens eruption, the sourceprocess that produced a sustained sequence of repetitive long-period (LP) seismic eventsalso produced impulsive broadband infrasonic signals in the atmosphere. To assesswhether the signals could be generated simply by seismic-acoustic coupling from theshallow LP events, we perform finite difference simulation of the seismo-acousticwavefield using a single numerical scheme for the elastic ground and atmosphere. Theeffects of topography, velocity structure, wind, and source configuration are considered.The simulations show that a shallow source buried in a homogeneous elastic solidproduces a complex wave train in the atmosphere consisting of P/SV and Rayleigh waveenergy converted locally along the propagation path, and acoustic energy originating fromthe source epicenter. Although the horizontal acoustic velocity of the latter isconsistent with our data, the modeled amplitude ratios of pressure to vertical seismicvelocity are too low in comparison with observations, and the characteristic differences inseismic and acoustic waveforms and spectra cannot be reproduced from a commonpoint source. The observations therefore require a more complex source process in whichthe infrasonic signals are a record of only the broadband pressure excitation mechanism ofthe seismic LP events. The observations and numerical results can be explained by amodel involving the repeated rapid pressure loss from a hydrothermal crack by ventinginto a shallow layer of loosely consolidated, highly permeable material. Heating bymagmatic activity causes pressure to rise, periodically reaching the pressure threshold forrupture of the ‘‘valve’’ sealing the crack. Sudden opening of the valve generates thebroadband infrasonic signal and simultaneously triggers the collapse of the crack,initiating resonance of the remaining fluid. Subtle waveform and amplitude variability ofthe infrasonic signals as recorded at an array 13.4 km to the NW of the volcano areattributed primarily to atmospheric boundary layer propagation effects, superimposedupon amplitude changes at the source. http://hdl.handle.net/2122/6059 Titolo: Changes in the VLP seismic source during the 2007 Stromboli eruption<br/><br/>Autori: Giudicepietro, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; D'Auria, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Martini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Caputo, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Peluso, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; De Cesare, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Orazi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Scarpato, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia<br/><br/>Abstract: Aim of this paper is to identify variations in Very-Long-Period (VLP) source associated with eruptive stylechanges at Stromboli volcano (Italy) and to retrieve information about the shallow plumbing system thatsustains the eruptive activity.We have considered a dataset of 74493 VLP events recorded during the period from January through August2007, when an effusive eruption occurred (February 27–April 2).We performed a polarization analysis of theentire dataset and divided the considered period into four sub-periods on the basis of polarizationcharacteristics. We then located the events and selected a subset of these events by applying a locationquality threshold. The high quality locations demonstrate that during the effusive eruption the VLP sourcesfirst moved downward and then moved southwestward.To retrieve information about the geometry of the structures where the source processes take place, wefurther consider a subset of events and estimate their source mechanisms by using a moment tensor sourcefunction (MTSF) inversion technique. Inversion of the waveforms of the VLP events that occurred onFebruary 27 allows us to obtain information about the dynamics of different source centroids distributedalong different portions of the shallow magmatic conduits. The structure defined by the locations and sourcemechanisms shows a greater complexity compared with previous studies and their time variations give aninsight into the kinematics of the eruption. 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. 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. http://hdl.handle.net/2122/6032 Titolo: Theoretical study on SO2 and ash volcanic plume retrievals using ground TIR camera. Sensitivity analysis and retrieval procedure developments<br/><br/>Autori: Corradini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Tirelli, C.; Università La Sapienza Roma; Gangale, G.; Università di Modena e Reggio Emilia; Pugnaghi, Sergio; Università di Modena e Reggio Emilia; Carboni, E.; Atmospheric, Oceanic, and Planetary Physics, Atmospheric, Oceanic, and Planetary Physics, Clarendon Laboratory, University of Oxford<br/><br/>Abstract: In this paper, a sensitivity analysis and procedure development for volcanic-plume sulfur dioxide and ash retrievals using ground thermal infrared camera have been carried out. The semiconductor device camera, considered as a reference, has a spectral range of 8–14 μm with noise equivalent temperature difference that is better than 100 mK at 300 K. The camera will be used to monitor and assess the hazards of Mt. Etna volcano to mitigate the risk and impact of volcanic eruptions on the civil society and transports. A minimum number of filters have been selected for sulfur dioxide (SO2) and volcanic ash retrievals.The sensitivity study has been carried out to determine the SO2 and volcanic ash minimum concentration detectable by the system varying the camera geometry and the atmospheric profiles. Results show a meaningful sensitivity increase considering high instrument altitudes and low camera-elevation angles. For all geometry configurations and monthly profiles, the sensitivity limit varies between 0.5 and 2 g · m−2 for SO2 columnar abundance and between 0.02 and 1 for ash optical depth. Two procedures to detect SO2 and ash, based on the least square fit method and on the brightness temperature difference (BTD) algorithm, respectively, have also been proposed. Results show that high concentration of atmospheric water vapor columnar content significantly reducesthe ash-plume effect on the BTD. A water vapor-correction procedure introduced improves the ash retrievals and the cloud discrimination in every season, considering all the camera geometries. http://hdl.handle.net/2122/5988 Titolo: Excess volatiles supplied by mingling of mafic magma at an andesite arc volcano<br/><br/>Autori: Edmonds, M.; COMET, National Centre for Earth Observation, Earth Sciences Department, University of Cambridge, Cambridge CB2 3EQ, UK; Aiuppa, A.; Dipartimento CFTA, Università di Palermo, Via archirafi 36, I-90123 Palermo, Italy; Humphreys, M.; Earth Sciences Department, University of Cambridge, Cambridge CB2 3EQ, UK; Moretti, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Giudice, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Martin, R. S.; Earth Sciences Department, University of Cambridge, Cambridge CB2 3EQ, UK; Herd, R. A.; School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK; Christopher, T.; Montserrat Volcano Observatory, Montserrat, West Indies<br/><br/>Abstract: We present the results of a study of volcanic gases at Soufrière Hills Volcano, Montserrat, which includes the first spectroscopic measurements of the major gas species CO2 and H2S at this volcano using a Multisensor Gas Analyzer System (MultiGAS) sensor. The fluxes of CO2 and H2S were 640–2750 t/d and 84–266 t/d, respectively, during July 2008, during a prolonged eruptive pause. The flux of CO2 issimilar to estimates for the entire arc from previous geochemical studies, while the measured H2S flux significantly alters our interpretation of the sulphur budget for this volcano. The fluxes of both sulphur and carbon show considerable excesses over that which can be supplied by degassing of erupted magma.We demonstrate, using thermodynamic models and published constraints on preeruptive volatile concentrations, that the gas composition and fluxes are best modeled by mixing between (1) gases derived from isobaric quenching of mafic magma against cooler andesite magma at depth and (2) gases derived from shallower rhyolitic interstitial melt within the porpyritic andesite. The escape of deep‐derived gases requires pervasive permeability or vapor advection extending to several kilometers depth in the conduit and magma storage system. These results provide more compelling evidence for both the contribution of unerupted mafic magma to the volatile budget of this andesitic arc volcano and the importance of the intruding mafic magma in sustaining the eruption. From a broader perspective, this study illustrates the importance and role ofunderplating mafic magmas in arc settings. These magmas play an important role in triggering and sustaining eruptions and contribute in a highly significant way to the volatile budget of arc volcanoes. http://hdl.handle.net/2122/5952 Titolo: Physical-Mathematical modeling and numerical simulations of stress-strain state in seismic and volcanic regions<br/><br/>Autori: Scandura, Danila<br/><br/>Abstract: The strain-stress state generated by faulting or cracking and influenced by the strong heterogeneity of the internal earth structure precedes and accompanies volcanic and seismic activity. Particularly, volcanic eruptions are the culmination of long and complex geophysical processes and physical processes which involve the generation of magmas in the mantle or in the lower crust, its ascent to shallower levels, its storage and differentiation in shallow crustal chambers, and, finally, its eruption at the Earth’s surface. Instead, earthquakes are a frictional stick-slip instability arising along pre-existing faults within the brittle crust of the Earth. Long-term tectonic plate motion causes stress to accumulate around faults until the frictional strength of the fault is exceeded. The study of these processes has been traditionally carried out through different geological disciplines, such as petrology, structural geology, geochemistry or sedimentology. Nevertheless, during the last two decades, the development of physical of earth as well as the introduction of new powerful numerical techniques has progressively converted geophysics into a multidisciplinary science. Nowadays, scientists with very different background and expertises such as geologist, physicists, chemists, mathematicians and engineers work on geophysics. As any multidisciplinary field, it has been largely benefited from these collaborations. The different ways and procedures to face the study of volcanic and seismic phenomena do not exclude each other and should be regarded as complementary.Nowadays, numerical modeling in volcanology covers different pre-eruptive, eruptive and post-eruptive aspects of the general volcanic phenomena. Among these aspects, the pre-eruptive process, linked to the continuous monitoring, is of special interest because it contributes to evaluate the volcanic risk and it is crucial for hazard assessment, eruption prediction and risk mitigation at volcanic unrest.large faults. The knowledge of the actual activity state of these sites is not only an academic topic but it has crucial importance in terms of public security and eruption and earthquake forecast. However, numerical simulation of volcanic and seismic processes have been traditionally developed introducing several simplifications: homogeneous half-space, flat topography and elastic rheology. These simplified assumptions disregards effects caused by topography, presence of medium heterogeneity and anelastic rheology, while they could play an important role in Moreover, frictional sliding of a earthquake generates seismic waves that travel through the earth, causing major damage in places nearby to the modeling procedureThis thesis presents mathematical modeling and numerical simulations of volcanic and seismic processes. The subject of major interest has been concerned on the developing of mathematical formulations to describe seismic and volcanic process. The interpretation of geophysical parameters requires numerical models and algorithms to define the optimal source parameters which justify observed variations. In this work we use the finite element method that allows the definition of real topography into the computational domain, medium heterogeneity inferred from seismic tomography study and the use of complex rheologies. Numerical forward method have been applied to obtain solutions of ground deformation expected during volcanic unrest and post-seismic phases, and an automated procedure for geodetic data inversion was proposed for evaluating slip distribution along surface rupture. http://hdl.handle.net/2122/5937 Titolo: Understanding stress and deformation in active volcanoes<br/><br/>Autori: Gudmundsson, A.; Univ. London Royal Holloway; Acocella, V.; Univ. Roma 3; Vinciguerra, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia<br/><br/>Abstract: No eruption, no caldera collapse, and no landslide can take place in a volcano unless its state of stress is suitable for the associated type of rock failure. The state of stress, in turn, results in deformation, and both stress and deformation depend on the mechanical properties of the rocks that constitute the volcano. Understanding stress and deformation in volcanoes is thus of fundamental importance for understanding unrest periods and for accurate forecasting volcano failure, such as may result in large-scale lateral and vertical collapses and eruptions. http://hdl.handle.net/2122/5892 Titolo: Structure and CO2 budget of Merapi volcano during inter-eruptive periods<br/><br/>Autori: Toutain, J. P.; Université de Toulouse; UPS (OMP); LMTG,; Sortino, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Baubron, J. C.; JcbConsulting; Richon, P.; CEA, DIF, Service Radiochimie Chimie Environnemen; Surono; DVGHM; Sumarti, S.; MVO – Merapi Volcanological Observatory<br/><br/>Abstract: Abstract Soil temperature and gas (CO2 concentration andflux) have been investigated at Merapi volcano (Indonesia)during two inter-eruptive periods (2002 and 2007). Preciseimaging of the summit crater and the spatial pattern ofdiffuse degassing along a gas traverse on the southern slopeare interpreted in terms of summit structure and majorcaldera organization. The summit area is characterized bydecreasing CO2 concentrations with distance from the 1932crater rim, down to atmospheric levels at the base of theterminal cone. Similar patterns are measured on anytransect down the slopes of the cone. The spatial distributionof soil gas anomalies suggests that soil degassing iscontrolled by structures identified as concentric historicalcaldera rims (1932, 1872, and 1768), which have undergonesevere hydrothermal self-sealing processes that dramaticallylower the permeability and porosity of soils.Temperature and CO2 flux measurements in soils near thedome display heterogeneous distributions which are consistentwith a fracture network identified by previousgeophysical studies. These data support the idea that thesummit is made of isolated and mobile blocks, whoseboundaries are either sealed by depositional processes or