ALBERT

Description: L’Italia e l’Indonesia hanno avviato nel 2005-2006 un progetto di cooperazione sulle tematiche della mitigazione del rischio vulcanico. Nell’ambito di questo progetto è stata individuata la zona ovest di Sumatra come area di intervento. In particolare è stato preso in considerazione il vulcanoMarapi. Questo vulcano ha avuto frequente attività eruttiva nelle ultime decine di anni. L’ultima eruzione si è verificata nel 2004. La sua attività, sebbene di moderata intensità, pone un problema di protezione civile, poiché dal 1980 ad oggi ha causato diversi feriti e alcune vittime tra i turisti che hanno visitato l’area craterica sommitale. Allo scopo di monitorare lo stato di attività del Marapi, nell’ambito del citato progetto è stata realizzata una rete sismica a larga banda composta da 4 stazioni e basata su sensori Guralp GMG-40T da 60s di periodo e su acquisitori di tipo GAIA2, prodotti presso l’Istituto Nazionale di Geofisica e Vulcanologia. La strumentazione è stata portata dall’Italia ed è stata installata da un gruppo di lavoro formato da italiani ed indonesiani. Oltre all’installazione della strumentazione in campagna è stato necessario allestire un vero e proprio Centro di Monitoraggio presso l’Osservatorio di Bukittinggi, in prossimità delle pendici nordoccidentali del vulcano, dotato di calcolatori per l’acquisizione, l’analisi dei dati e la loro archiviazione. Il sistema per ilmonitoraggio sismologico realizzato alMarapi costituisce un importante strumento di prevenzione del rischio associato all’attività di questo vulcano e sta permettendo di creare un ricco data set utile a caratterizzare la sismicità della struttura vulcanica e dell’area circostante. Da un’analisi preliminare dei dati registrati nel periodo 19/10/2006 - 24/11/2008 si evidenzia che il vulcanomanifesta una sismicità di tipo VT ed LP. Nell’ agosto 2007 sono stati inoltre registrati segnali probabilmente attribuibili a modesta attività esplosiva nell’area sommitale. Italy and Indonesia started a cooperation project in 2005-2006 to cover issues for the mitigation of volcanic risk. In this project, the west area of Sumatra was identified as the area for intervention. In particular, the Marapi volcano was considered. This volcano has shown frequent eruptive activity over recent decades, with the last eruption occurring in 2004. Although its activity is of moderate intensity, it creates a civil protection problem, because since 1980 it has resulted in several injuries and a number of deaths among the tourists who visit the summit crater area. To monitor the activity of Marapi volcano as part of this project, a broadband seismic network has been implemented that consists of four stations based on Guralp GMG 40T sensors with period of 60 s and on GAIA2 data-loggers, which are produced at the INGV. The instrumentation was brought from Italy and was installed by a working group comprising Italians and Indonesians. In addition to the instrumentation in the field, it was necessary to set up a monitoring centre in the Bukittinggi Observatory, which is near the north-western slopes of the Marapi volcano. This is equipped with computers for data acquisition, analysis and archiving. The system for seismological monitoring that has been realized atMarapi volcano is an important tool in the prevention of the risk associated with this volcano, and it is providing a rich dataset that will be of great use for the characterization of the seismicity of the Marapi volcanic structure and the surrounding area. A preliminary analysis of the data recorded during the period 19/10/2006 - 24/11/2008 evidences that the volcano shows VT and LP seismicity. In August 2007 were also recorded signals probably attributable to small explosive activity in the summit area.

Description: INGV Istituto Nazionale di Geofisica e Vulcanologia

Description: Published

Description: 5-21

Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive

Description: N/A or not JCR

Description: open

Description: We have analyzed a focal mechanism data set for Mount Vesuvius, consisting of 197 focal mechanisms of events recorded from 1999 to 2012. Using different approaches and a comparison between observations and numerical models, we have determined the spatial variations in the stress field beneath the volcano. The main results highlight the presence of two seismogenic volumes characterized by markedly different stress patterns. The two volumes are separated by a layer where the seismic strain release shows a significant decrease. Previous studies postulated the existence, at about the same depth, of a ductile layer allowing the spreading of the Mount Vesuvius edifice. We interpreted the difference in the stress pattern within the two volumes as the effect of a mechanical decoupling caused by the aforementioned ductile layer. The stress pattern in the top volume is dominated by a reverse faulting style, which agrees with the hypothesis of a seismicity driven by the spreading process. This agrees also with the persistent character of the seismicity located within this volume. Conversely, the stress field determined for the deep volume is consistent with a background regional field locally perturbed by the effects of the topography and of heterogeneities in the volcanic structure. Since the seismicity of the deep volume shows an intermittent behavior and has shown to be linked to geochemical variations in the fumaroles of the volcano, we hypothesize that it results from the effect of fluid injection episodes, possibly of magmatic origin, perturbing the pore pressure within the hydrothermal system.

Description: Published

Description: 1181–1199

Description: 4T. Fisica dei terremoti e scenari cosismici

Description: 2V. Dinamiche di unrest e scenari pre-eruttivi

Description: 5V. Sorveglianza vulcanica ed emergenze

Description: JCR Journal

Description: restricted

Description: We present a comprehensive processing tool for the real-time analysis of the source mechanism of very long period (VLP) seismic data based on waveform inversions performed in the frequency domain for a point source. A search for the source providing the best-fitting solution is conducted over a three-dimensional grid of assumed source locations, in which the Green’s functions associated with each point source are calculated by finite differences using the reciprocal relation between source and receiver. Tests performed on 62 nodes of a Linux cluster indicate that the waveform inversion and search for the best-fitting signal over 100,000 point sources require roughly 30 s of processing time for a 2-min-long record. The procedure is applied to post-processing of a data archive and to continuous automatic inversion of real-time data at Stromboli, providing insights into different modes of degassing at this volcano

Description: Published

Description: L04301

Description: reserved

Description: An accelerating process of ground deformation that began 10 years ago is currently affecting the Campi Flegrei caldera. The deformation pattern is here explained with the overlapping of two processes: short time pulses that are caused by injection of magmatic fluids into the hydrothermal system; and a long time process of heating of the rock. The short pulses are highlighted by comparison of the residuals of ground deformation (fitted with an accelerating polynomial function) with the fumarolic CO2/CH4 and He/CH4 ratios (which are good geochemical indicators of the arrival of magmatic gases). The two independent datasets show the same sequence of five peaks, with a delay of ∼200 days of the geochemical signal with respect to the geodetic signal. The heating of the hydrothermal system, which parallels the long-period accelerating curve, is inferred by temperature–pressure gas geoindicators. Referring to a recent interpretation that relates variations in the fumarolic inert gas species to open system magma degassing, we infer that the heating is caused by enrichment in water of the magmatic fluids and by an increment in their flux. Heating of the rock caused by magmatic fluids can be a central factor in triggering unrest at calderas.

Description: Published

Description: 58-67

Description: 2V. Dinamiche di unrest e scenari pre-eruttivi

Description: JCR Journal

Description: restricted

Description: INGV

Description: Published

Description: 5.9. TTC - Sistema web

Description: open

Description: THE ISTITUTO NAZIONALE DI GEOFISICA E VULCANOLOGIA (INGV) AND THE ITALIAN DEPARTMENT FOR CIVIL DEFENSE (DPC)

Description: Published

Description: 1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive

Description: open

Description: On 10 September 2005 at 1711 LT (1511 UT) a loud boom was heard on the Ischia island. A clear seismic signal was also recorded by the seismic monitoring network of the Neapolitan volcanic areas (Ischia, Campi Flegrei, and Mount Vesuvius) and on a regional station (Mount Massico). On the basis of the seismic recordings and on acoustic phenomena reports, we relate this event to the atmospheric explosion (airburst) of a bolide about 15 km SW of Ischia at an elevation of about 11.5 km. The location has been obtained through nonlinear traveltime inversion in a realistic atmospheric model including wind effects. We show, using statistical estimators, how the traveltime pattern is due to both atmospheric winds and the bolide trajectory. Using the same reasoning we discard a human origin (supersonic jet or sea-air missile). In addition, we also propose a new algorithm for fast acoustic traveltime computation for a supersonic moving source.

Description: Published

Description: B10307

Description: reserved

Description: On 5 April 2003 at 07:13 GMT (09:13 local time) a violent vulcanian explosion occurred at Stromboli volcano. At the time of the event an eruptive crisis was ongoing at the volcano with a lava flow outpouring along the Sciara del Fuoco flank. The seismic signals related to the event were recorded by 8 permanent broadband stations and gives information about the eruption kinematics. An ultra-longperiod signal (period 〉 20 s), that we interpret as the effect of the ground tilt on the broadband sensors, starts about 4 min before and terminates about 1 min after the explosion. On the basis of the radial pattern of tilt directions we conclude that this signal is the effect of the deformation of the volcanic edifice, due to the rapid rising of a batch of magma, its ejection and the magma column readjustment. About 1 min before the explosion we observe an high frequency signal (period 〈 0.1 s) that we believe to be related to the vesiculation of the rising batch of gas-rich magma. At 07:13:35 GMT a powerful very-long-period signal (period 2 20 s), marking the onset of the explosive fragmentation, is recorded. This is confirmed by a blast wave following few seconds later. The remaining seismic signal (more than 3 min), shows an higher frequency content being related only to the fall of ballistic ejecta and to landslides along Sciara del Fuoco.We propose the implementation of an early warning system for the short-term forecast of such explosions, based on the real-time automatic detection of the tilt signals preceding such events.

Description: Published

Description: L08308

Description: reserved

Description: In this article we report on the implementation of an automatic system for discriminating landslide seismic signals on Stromboli island (southern Italy). This is a critical point for monitoring the evolution of this volcanic island, where at the end of 2002 a violent tsunami occurred, triggered by a big landslide. We have devised a supervised neural system to discriminate among landslide, explosion-quake, and volcanic microtremor signals. We first preprocess the data using a compact representation of the seismic records. Both spectral features and amplitude-versus-time information have been extracted from the data to characterize the different types of events. As a second step, we have set up a supervised classification system, trained using a subset of data (the training set) and tested on another data set (the test set) not used during the training stage. The automatic system that we have realized is able to correctly classify 99% of the events in the test set for both explosion-quake/ landslide and explosion-quake/microtremor couples of classes, 96% for landslide/ microtremor discrimination, and 97% for three-class discrimination (landslides/ explosion-quakes/microtremor). Finally, to determine the intrinsic structure of the data and to test the efficiency of our parameterization strategy, we have analyzed the preprocessed data using an unsupervised neural method. We apply this method to the entire dataset composed of landslide, microtremor, and explosion-quake signals. The unsupervised method is able to distinguish three clusters corresponding to the three classes of signals classified by the analysts, demonstrating that the parameterization technique characterizes the different classes of data appropriately.

Description: Published

Description: 1230-1240

Description: reserved

Description: Il sito web dell’Osservatorio Vesuviano (INGV), istituito nella seconda metà del 1997, ha acquisito nel maggio del 2002 la sua attuale fisionomia, a seguito di una sostanziale ristrutturazione. Allo scopo di verificare il gradimento e l’impatto che il sito ha presso il pubblico è stato installato un software di statistiche web e di monitoraggio degli accessi. La scelta del software è stata improntata a criteri di semplicità d’uso e di economicità. Dopo una ricerca tra i prodotti più diffusi è stato scelto il pacchetto Awstats versione 6.4 (http://awstats.sourceforge.net/) che consente di ottenere tutte le informazioni di interesse e risulta di facile implementazione. AWStats è un’ applicazione open source, distribuita sotto la GNU General Public License, che analizza i file di log prodotti da un web server presentando i dati in forma grafica di facile lettura. L’applicazione è sviluppata in perl e php e funziona con vari web server, quali Apache o IIS.

Description: Published

Description: 5.9. TTC - Sistema web

Description: open