http://hdl.handle.net/2122/261 2013-06-20T07:56:05Z http://hdl.handle.net/2122/8667 Title: Terrain characterization and structural control of the Auca Mahuida volcanism (Neuquén Basin, Argentina) Authors: Ventura, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; De Ritis, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Longo, M.; Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, La Plata, Argentina; Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Geomorphometric parameters (slope, aspect, valley depth, and areal density of cones) derived from a moderate resolution digital elevation model with a grid spacing of 100 m are used in an attempt to interpret the tectonic/structural features related to surface deformation in the Auca Mahuida volcanic terrain (Neuquén Basin, Argentina). The Auca Mahuida (2.03–0.88 Ma) is the southernmost volcanic field of the Payenia volcanic province, in the Andean foreland. The foreland is subjected to an E–W compression related to the eastward migration of the N–S striking thrust front of the Andes. The geomorphometric analysis indicates that the Auca Mahuida consists of a basal, E–W elongated lava field with monogenic vents and a summit, polygenic, also E–W elongated, cone. A N100◦E striking fault controls the southern flank of the field, which is also affected by scarps related to erosional and gravity-controlled processes. The drainage network shows a pseudo-radial pattern around the summit cone, and the Auca Mahuida’s deepest valley is structurally controlled by a NNW–SSE striking fault affecting the sedimentary basement. The volcanic field lies on a NE to E dipping substratum. The areal distribution of the monogenic cones is consistent with ascent of magmas along E–W striking fractures, and with elastic models of a pressurized hole (magma chamber) subjected to an E–W compression. At Auca Mahuida, the ascent of melts from the mantle is controlled, in the overriding crust, by tectonic structures formed in response to the E–W compression of the Andes. 2012-10-31T23:00:00Z http://hdl.handle.net/2122/8654 Title: A second order accurate numerical model for multiphase underexpanded volcanic jets Authors: Carcano, S.; MOX – Modelling and Scientific Computing, Dipartimento di Matematica F. Brioschi, Politecnico di Milano, Milano, Italy; Bonaventura, L.; MOX – Modelling and Scientific Computing, Dipartimento di Matematica F. Brioschi, Politecnico di Milano, Milano, Italy; Neri, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Esposti Ongaro, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia Abstract: An improved version of the PDAC (Pyroclastic Dispersal Analysis Code) numerical model for the simulation of multiphase volcanic flows is presented and validated for the simulation of multiphase volcanic jets in supersonic regimes. The present version of PDAC includes second-order time and space discretizations and fully multidimensional advection discretizations, in order to reduce numerical diffusion and enhance the accuracy of the original model. The resulting numerical model is tested against the problem of jet decompression in both two and three dimensions. For homogeneous jets, numerical results show a good quantitative agreement with experimental results on the laboratory scale in terms of Mach disk location (Lewis and Carlson, 1964). For multiphase jets, we consider monodisperse and polydisperse mixtures of particles with different diameter. For fine particles, for which the pseudogas limit is valid, the multiphase model correctly reproduces predictions of the pseudogas model. We obtain that particles are in mechanical and thermal equilibrium with the gas phase and the jet decompression structure is in quantitative agreement with pseudogas results (Ogden et al., 2008b). For both fine and coarse particles, we measure the importance of multiphase effects with relation to the characteristic time scales of multiphase jets and we quantify how particles affect the average jet dynamics in terms of pressure, mixture density, vertical velocity and temperature. Furthermore, time dependent vent conditions are introduced, in order to achieve numerical simulation of eruption regimes characterized by transient jet behaviour. We show how in case of rapid change in vent conditions, volcanic jet structures do not evolve through a succession of steady state configurations and the transition between different flow conditions can result in the collapse of the volcanic column. 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8565 Title: VULCANOLOGIA E SISMOLOGIA: IL GIAPPONE E NAPOLI Authors: Cubellis, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia Editors: Tamburello, Adolfo Abstract: Il Giappone dista da Napoli 10.000 km ma l’arcipelago giapponese ha in comune con il Golfo di Napoli e la Campania Felix dei Romani la genesi geologica, in quanto sono stati formati da processi geodinamici del tutto simili, come la natura vulcanica dei suoli, il morbido paesaggio dei coni e dei crateri vulcanici, le manifestazioni fumaroliche delle «solfatare» ed il termalismo quali spie della presenza di masse di magma intrappolate nella crosta a piccola profondità, la sismicità, chiara manifestazione della non sopita dinamica di questi territori. Due terre con tali caratteristiche non potevano non incontrarsi per i comuni interessi nella crescita della conoscenza dei fenomeni vulcanici e sismici e per la mitigazione dei loro effetti sulle popolazioni esposte. Non a caso Italia e Giappone saranno nella seconda metà dell’Ottocento i paesi più avanzati nello studio dei terremoti e dei vulcani. 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8403 Title: Automatic real-time detection and location of Very Long Period events at Stromboli Authors: D'Auria, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Giudicepietro, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Martini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; De Cesare, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Scarpato, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia Abstract: Signals with Very Long Periods (VLP) (1-60s) have been recorded on many active volcanoes. They are related with various dynamical processes in the volcano feeding system. Stromboli was one of the first volcanoes where such signals have been observed and analyzed. After the beginning of an anomalous eruptive activity in December 2002, a permanent broadband seismic network was deployed, by INGV-Osservatorio Vesuviano, in January 2003. Currently the network consists in 11 stations. Seismic data are continuously acquired by the INGV-Osservatorio Vesuviano in Naples, where they are analyzed in real time and stored. Preliminary results are immediately published on public web pages. In this paper we focus on the method used for detecting and locating VLP events. Such events have not a clear onset, so classical methods for automatic picking and location fails. Compared to common earthquakes signals, VLPs shows a high waveform coherence among different stations and a clear radial polarization toward the hypocenter. Using these features, hypocenters may be found searching for the points in the space having the highest coherence in the radial component. This is quantified using a modified semblance function over band-pass filtered (2-20 s) signals. The point having the highest semblance function value is the hypocenter. The semblance function is computed continuously for 10 s time windows over a regular grid centered on Stromboli, having a volume of 8000x8000x2000 m and a spacing of 100x100x50 m. VLP events are detected when the maximum value of the semblance function exceed a given threshold value. This task require heavy computation efforts. For this reason we use a 64 processor parallel computer for performing real-time analysis. 2004-03-31T22:00:00Z http://hdl.handle.net/2122/8396 Title: The Stromboli Volcano Broadband Seismic Monitoring System Authors: Martini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Giudicepietro, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; De Cesare, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; D'Auria, L.; 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; Cattaneo, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Badiali, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione AC, Roma, Italia Abstract: After the beginning of the eruptive crisis that has interested the Stromboli volcano (Southern Italy) at the end of 2002, starting the second half of January 2003 it has been installed on the island a centralized broadband seismic network, at present composed by 11 stations, all equipped with Guralp CMG-40T (0,02-60 s period). The network is one of the first designed to monitor and analyze in real time the very long periods (VLP) events, which are produced, in the case of the Stromboli volcano, at a rate of hundreds per day. The disposition of the stations has been chosen in order to realize an azimuth and distance homogeneously distribution regarding possible seismic sources situated along the upper part of feeding system of the volcano. The network shows a distribution of stations that encircle the volcanic structure to various levels regarding the area of craters and the eruptive vents, with distance of the stations from the emission centers that vary between some hundreds of meters to about 2 kilometers. The signals, acquired using 24 bits A/D data loggers designed by INGV - CNT, are transmitted via UHF radiomodems to two intermediate centralization sites . The first one is the Observatory of S. Vincenzo where are centralized the stations installed on the northern side of the island, the second is the Observatory INGV in the Lipari island, where are centralized all the other stations. From these two intermediate centralization sites the data are transmitted via TCP/IP protocol, using the Italian scientific-academic internet network GARR, towards the INGV monitoring centers of Catania and Observatory Vesuviano (Naples), where the broadband signals are monitored and processed, using a 64 CPU computer cluster to perform the VLP real-time analysis. 2004-03-31T22:00:00Z http://hdl.handle.net/2122/8394 Title: Volcanoes: effusions and explosions. Interactive exhibits to understand how volcanoes work Authors: C. Nostro, L. Freda, C. Castellano, L. Arcoraci, E. Baroux, M. Pignone, A. Tertulliani, M. De Lucia, M. Di Vito, P. Landi, P. Madonia, M. Martini, R. Nave, M. Neri, P. Scarlato, J. Taddeucci, R. Moschillo, S. Tarquini, G. Vilardo, A. Bonforte, L. Calderone, F. Cannavò, W. De Cesare, P. Ficeli, S. Inguaggiato, M. Mattia, G. Puglisi, S. Morici, D. Reitano, D. Richichi, G. Scarpato, B. Angioni, F. Di Laura, S. Palone, D. Riposati; Istituto Nazionale di Geofisica e Vulcanologia, Sezione AC, Roma, Italia Abstract: The Educational & Outreach Group (EOG) of the Istituto Nazionale di Geofisica & Vulcanologia created a portable museum to provide educational opportunities in volcanology, volcanic risk and Earth science for students and visitors. The EOG developed this project for the "Festival della Scienza", organized in Genoa, Italy, in October - November, 2007, which was a parade of over 200 events, including scientific and technological exhibitions, workshops, meetings, lectures, books and video presentations. In this museum visitors can successively see many posters and movies and play with interactive exhibits. A little 3D-movie shows the Big Bang, the formation of Solar System and, in particular the formation of the Earth. Many interactive exhibits illustrate why, where and when earthquakes and volcanic eruptions occur around the world and allow to introduce the visitor to the plate tectonics theory. A 3D magnetic plate tectonic puzzle can be put down and reconstructed by visitors to understand the Earth’s surface configuration. Then two other 3D Earth models show what drives the plates and the inner Earth structure. An interactive program illustrates where and when earthquakes and volcanic eruptions occur in accelerated time on maps of various areas around the world. Playing with a block diagram it is possible to produce an earthquake along a 1 meter long strike slip fault in a destroying all the man-made constructions close to it. A little movie introduces to volcanoes’ world. Two small interactive exhibits allow visitors to understand the mechanism for the explosive and the effusive eruptions. Two other exciting interactive exhibits allow visitors to “create” two different eruptions: the explosive and the effusive ones. It is possible to get inside a volcano (a 2 meter high interactive exhibit) to attend an eruption from the magmatic chamber to the Earth surface. A big hall is completed dedicated to Italian volcanoes (Vesuvio, Campi Flegrei, Etna, Stromboli, Vulcano, Colli Albani); some of them are reproduced with 3D models or described by short movies. The museum finishes with the visit of the volcanic survey hall of Stromboli, seeing - in real time - seismic data, three different webcams, geochemical and strain data. The INGV Museum had remarkably successful, reaching more than 7,500 children and adults yet in 13 days, also thanks to 30 volcanologists as very special guides. The Educational & Outreach Group: M. Pignone, A. Tertulliani, M. De Lucia, M. Di Vito, P. Landi, P. Madonia, M. Martini, R. Nave, M. Neri, P. Scarlato, J. Taddeucci, R. Moschillo, S. Tarquini, G. Vilardo, A. Bonforte, L. Calderone, F. Cannavò, W. De Cesare, P. Ficeli, S. Inguaggiato, M. Mattia, G. Puglisi, S. Morici, D. Reitano, D. Richichi, G. Scarpato, B. Angioni, F. Di Laura, S. Palone, D. Riposati 2009-03-31T22:00:00Z http://hdl.handle.net/2122/8373 Title: An analytical model for gas overpressure in slug-driven explosions: Insights into Strombolian volcanic eruptions Authors: Del Bello, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Llewellin, E. W.; University of Durham; Taddeucci, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Scarlato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Lane, S.; Lancaster University Abstract: Strombolian eruptions, common at basaltic volcanoes, are mildly explosive events that are driven by a large bubble of magmatic gas (a slug) rising up the conduit and bursting at the surface. Gas overpressure within the bursting slug governs explosion dynamics and vigor and is the main factor controlling associated acoustic and seismic signals. We present a theoretical investigation of slug overpressure based on magma-static and geometric considerations and develop a set of equations that can be used to calculate the overpressure in a slug when it bursts, slug length at burst, and the depth at which the burst process begins. We find that burst overpressure is controlled by two dimensionless parameters: V′, which represents the amount of gas in the slug, and A′, which represents the thickness of the film of magma that falls around the rising slug. Burst overpressure increases nonlinearly as V′ and A′ increase. We consider two eruptive scenarios: (1) the “standard model,” in which magma remains confined to the vent during slug expansion, and (2) the “overflow model,” in which slug expansion is associated with lava effusion, as occasionally observed in the field. We find that slug overpressure is higher for the overflow model by a factor of 1.2–2.4. Applying our model to typical Strombolian eruptions at Stromboli, we find that the transition from passive degassing to explosive bursting occurs for slugs with volume >24–230 m3, depending on magma viscosity and conduit diameter, and that at burst, a typical Strombolian slug (with a volume of 100–1000 m3) has an internal gas pressure of 1–5 bars and a length of 13–120 m. We compare model predictions with field data from Stromboli for low-energy “puffers,” mildly explosive Strombolian eruptions, and the violently explosive 5 April 2003 paroxysm. We find that model predictions are consistent with field observations across this broad spectrum of eruptive styles, suggesting a common slug-driven mechanism; we propose that paroxysms are driven by unusually large slugs (large V′). 2012-02-09T23:00:00Z http://hdl.handle.net/2122/8326 Title: The morphological evolution of the Sciara del Fuoco since 1868: reconstructing the effusive activity at Stromboli volcano Authors: Marsella, M.; Dip. Ingegneria Civile, Edile, Ambientale, Univ. “La Sapienza”, Roma, Italy; Baldi, P.; Settore Geofisica, Dip. Fisica, University of Bologna, Bologna, Italy; Coltelli, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Fabris, M.; Dip. Architettura, Urbanistica e Rilevamento, University of Padova, Padova, Italy Abstract: The morphological evolution of the Sciara del Fuoco, Stromboli, is described from a time series dataset formed by Digital Elevation Models and orthophotos derived by digitising historical contour maps compiled in 1868 and 1937 and by processing data from aerial surveys carried out between 1954 and 2009. All maps were coregistered in the same reference system and used to build a quantitative reconstruction of the morphological changes of the Sciara del Fuoco slope. The changes mainly relate to the emplacement of many lava flows and their successive erosion. A comparative quantitative analysis yields estimates of areas and volumes of the lava fields formed on the sub-aerial part of the Sciara del Fuoco during a number of effusive events between 1937 and 2001, some of them never assessed before. The results of the analysis constrain the interpretation of the evolution and the magnitude of the recent effusive activity at the Stromboli volcano. Despite some uncertainties due to widely spaced observation periods, the results integrate all available topographic knowledge and contribute to an understanding of the main characteristics of the recent effusive eruptive styles at Stromboli volcano. 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8311 Title: Multiphase flow dynamics of pyroclastic density currents during the May 18, 1980 lateral blast of Mount St. Helens Authors: Esposti Ongaro, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Clarke, A. B.; School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA; Voight, B.; Department of Geosciences, Penn State University, University Park, Pennsylvania, USA; Neri, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Widiwijayanti, C.; Earth Observatory of Singapore, Nanyang Technological University, Singapore Abstract: The dynamics of the May 18, 1980 lateral blast at Mount St. Helens, Washington (USA), were studied by means of a three-dimensional multiphase flow model. Numerical simulations describe the blast flow as a high-velocity pyroclastic density current generated by a rapid expansion (burst phase, lasting less than 20 s) of a pressurized polydisperse mixture of gas and particles and its subsequent gravitational collapse and propagation over a rugged topography. Model results show good agreement with the observed large-scale behavior of the blast and, in particular, reproduce reasonably well the front advancement velocity and the extent of the inundated area. Detailed analysis of modeled transient and local flow properties supports the view of a blast flow led by a high-speed front (with velocities between 100 and 170 m/s), with a turbulent head relatively depleted in fine particles, and a trailing, sedimenting body. In valleys and topographic lows, pyroclasts accumulate progressively at the base of the current body after the passage of the head, forming a dense basal flow depleted in fines (less than 5 wt.%) with total particle volume fraction exceeding 10−1 in most of the sampled locations. Blocking and diversion of this basal flow by topographic ridges provides the mechanism for progressive current unloading. On ridges, sedimentation occurs in the flow body just behind the current head, but the sedimenting, basal flow is progressively more dilute and enriched in fine particles (up to 40 wt.% in most of the sampled locations). In the regions of intense sedimentation, topographic blocking triggers the elutriation of fine particles through the rise of convective instabilities. Although the model formulation and the numerical vertical accuracy do not allow the direct simulation of the actual deposit compaction, present results provide a consistent, quantitative model able to interpret the observed stratigraphic sequence. 2012-06-25T22:00:00Z http://hdl.handle.net/2122/8307 Title: How do volcanic rift zones relate to flank instability? Evidence from collapsing rifts at Etna Authors: Ruch, J.; Dipartimento Scienze Geologiche, Università Roma Tre, Roma, Italy; Pepe, S.; National Research Council (CNR), Istituto per il Rilevamento Elettromagnetico dell'Ambiente (IREA), Napoli, Italy; Casu, F.; National Research Council (CNR), Istituto per il Rilevamento Elettromagnetico dell'Ambiente (IREA), Napoli, Italy; Acocella, V.; Dipartimento Scienze Geologiche, Università Roma Tre, Roma, Italy; Neri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Solaro, G.; National Research Council (CNR), Istituto per il Rilevamento Elettromagnetico dell'Ambiente (IREA), Napoli, Italy; Sansosti, E.; National Research Council (CNR), Istituto per il Rilevamento Elettromagnetico dell'Ambiente (IREA), Napoli, Italy Abstract: Volcanic rift zones, characterized by repeated dike emplacements, are expected to delimit the upper portion of unstable flanks at basaltic edifices. We use nearly two decades of InSAR observations excluding wintertime acquisitions, to analyze the relationships between rift zones, dike emplacement and flank instability at Etna. The results highlight a general eastward shift of the volcano summit, including the northeast and south rifts. This steadystate eastward movement (1-2 cm/yr) is interrupted or even reversed during transient dike injections. Detailed analysis of the northeast rift shows that only during phases of dike injection, as in 2002, does the rift transiently becomes the upper border of the unstable flank. The flank's steady-state eastward movement is inferred to result from the interplay between magmatic activity, asymmetric topographic unbuttressing, and east-dipping detachment geometry at its base. This study documents the first evidence of steady-state volcano rift instability interrupted by transient dike injection at basaltic edifices. 2012-09-18T22:00:00Z