http://hdl.handle.net/2122/276 Wed, 22 May 2013 21:46:29 GMT 2013-05-22T21:46:29Z http://hdl.handle.net/2122/8652 Title: A Multidisciplinary Study of the DPRK Nuclear Tests Authors: Carluccio, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Giuntini, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Materni, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Chiappini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Bignami, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; D'Ajello Caracciolo, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Pignatelli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Stramondo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Console, R.; Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: The Democratic People Republic of Korea announced two underground nuclear tests carried out in their territory respectively on October 9th, 2006 and May 25th, 2009. The scarce information on the precise location and the size of those explosions has stimulated various kinds of studies,mostly based on seismological observations, by several national agencies concerned with theNuclear Test Ban Treaty verification.Weanalysed the available seismological data collected through a global high-quality network for the two tests. After picking up the arrival times at the various stations, a standard location program has been applied to the observed data. If we use all the available data for each single event, due to the different magnitude and different number of available stations, the locations appear quite different. On the contrary, if we use only the common stations, they happen to be only few km apart from each other and within their respective error ellipses. A more accurate relative location has been carried out by the application of algorithms such as double difference joint hypocenter determination (DDJHD) and waveform alignment. The epicentral distance between the two events obtained by these methods is 2 km, with the 2006 event shifted to the ESE with respect to that of 2009. We then used a dataset of VHR TerraSAR-X satellite images to detect possible surface effects of the underground tests. This is the first ever case where these highly performing SAR data have been used to such aim. We applied InSAR processing technique to fully exploit the capabilities of SAR data to measure very short displacements over large areas. Two interferograms have been computed, one co-event and one post-event, to remove possible residual topographic signals. A clear displacement pattern has been highlighted over a mountainous area within the investigated region, measuring a maximum displacement of about 45 mm overall the relief. Hypothesizing that the 2009 nuclear test had been carried out close to the area where the displacement has been observed through the DInSAR technique, its relation with the epicenter location obtained through seismological processing has been discussed as a possible alternative hypothesis with respect to the preferred solutions reported by the nuclear explosion database (NEDB). The distance of about 10 km between the two places can be considered acceptable in light of the possible systematic location shifts commonly observed in the seismological practice over a global scale. The difference between the mb magnitudes of the two tests could reflect differences in geological conditions of the two test sites, even if the yield of the two explosions had been the same. Fri, 28 Dec 2012 23:00:00 GMT http://hdl.handle.net/2122/8652 2012-12-28T23:00:00Z http://hdl.handle.net/2122/8649 Title: Digital signal processing and numerical analysis for radar in geophysical applications Authors: Molina, M. G.; Dpto. de Ciencias de la Computación, Facultad de Ciencias Exactas y Tecnología (FACET), Universidad Nacional de Tucumán (UNT), Av. Independencia 1800, Tucumán, Argentina; Cabrera, M. A.; Laboratorio de Telecomunicaciones, Dpto. de Electrónica Electricidad y Computación, FACET, UNT, Av. Independencia 1800, Tucumán, Argentina; Ezquer, R. G.; Laboratorio de Ionósfera, Dpto. de Física, FACET, UNT, Av. Independencia 1800, Tucumán, Argentina; Fernandez, P. M.; Dpto. de Ciencias de la Computación, Facultad de Ciencias Exactas y Tecnología (FACET), Universidad Nacional de Tucumán (UNT), Av. Independencia 1800, Tucumán, Argentina; Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Numerical solutions for signal processing are described in this work as acontribution to study of echo detection methods for ionospheric sounder design. The ionospheric sounder is a high frequency radar for geophysical applications. The main detection approach has been done by implementing the spread-spectrum techniques using coding methods to improve the radar’s range resolution by transmitting low power. Digital signal processing has been performed and the numerical methods were checked. An algorithm was proposed and its computational complexity was calculated. The proposed detection process combines two channels correlations with the local code and calculates threshold (Vt) by statistical evaluation of the background noise to design a detection algorithm. The noisy signals treatment was performed depending on the threshold and echo amplitude. In each case, the detection was improved by using coherent integration. Synthetic signals, close loop and actual echoes, obtained from the Advanced Ionospheric Sounder (AIS-INGV) at Rome Ionospheric Observatory, were used to verify the process. The results showed that, even in highly noisy environments, the echo detection is possible. Given that these are preliminary results, further studies considering data sets corresponding to other geophysical conditions are needed. Tue, 14 May 2013 22:00:00 GMT http://hdl.handle.net/2122/8649 2013-05-14T22:00:00Z http://hdl.handle.net/2122/8551 Title: GIS Methodology to Assess Landslide Susceptibility: Application to a River Catchment of Central Italy Authors: Leoni, G.; Consultant Geologist,; Barchiesi, F.; Roma Tre University; Catallo, F.; Roma Tre University; Dramis, F.; Roma Tre University; Fubelli, G.; Roma Tre University; Lucifora, S.; Roma Tre University; Mattei, M.; Roma Tre University; Pezzo, G.; Department of Geological Sciences, Roma Tre University; Puglisi, C.; ENEA, C.R. Casaccia Abstract: This paper illustrates a geographic information system (GIS) supported methodology for the assessment of landslide susceptibility. The methodology involves four operational steps: survey, site analysis, macro- area analysis and susceptibility analysis . The Survey includes the production (or acquisition) of a large-scale litho-technical map, a large-scale geomorphological map, a detailed inventory of past and present land- slide events, and a high resolution DTM (Digital Terrain Model. Site analysis leads to the definition of discriminating parameters (commonly, lithological and morphometric conditions necessary but not suffi- cient to trigger a landslide of a given type) and predisposing factors (conditions that worsen slope stability but are not sufficient to trigger a landslide of a given type in the absence of discriminating parameters ). The different predisposing factors are subdivided into classes, whose intervals are established by descriptive, statistical analysis of landslide inventory data. A numerical index, based on the frequency of landslide occurrence, quantifies the contribution of each class to slope instability. Macro-area analysis includes the generation of Litho-Morphometric Units (LMU) by overlaying discrimina- ting parameters , manual drawing of LMU envelopes ( macro-areas ), generation of predisposing factor maps from the spatial distribution of predisposing factors , and heuristic weighting of predisposing factor indices. Susceptibility analysis includes the generation of Homogeneous Territorial Units (HTU) by overlaying macro- areas and predisposing factor maps , and the application of a susceptibility function to the different HTU. The resulting values are normalized before the generation of the landslide susceptibility maps . The methodo- logy has been applied to the Fiumicino River catchment, located in the western side of Latium Apennine (Central Italy) between 200 and 1300 m a.s.l. and developed on Late Miocene calcarenites, sandstones with clay intercalations, and marls. The resulting landslide susceptibility maps will be employed in envi- ronmental management. They also represent the preliminary step for the assessment of landslide hazard and risk Sun, 22 Jan 2012 23:00:00 GMT http://hdl.handle.net/2122/8551 2012-01-22T23:00:00Z http://hdl.handle.net/2122/8359 Title: Studio e realizzazione di un protocollo di compressione dati per reti di sensori sismici Authors: Larocca, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia Abstract: Abstract Permanent seismic network management, in a country defined by active volcanoes, as well as a tectonic faults network, involve evaluating a great number of working and efficiency parameters, especially when risks are of a different nature and can cause economic damage to the local region. One example is the Permanent Seismic Net managed by the Istituto Nazionale di Geofisica e Vulcanologia(INGV), Catania Section, in Italy, which comprises about sixty seismic stations, using analogical and digital technology, located around Mt. Etna, the Peloritani and Hyblean areas, southern Calabria and in the Aeolian archipelago. Digital technology enables increasing management performance, signal to noise ratio and firmness, allowing gradual upgrades from analogical to digital stations. On the other hand, it introduces some new problems such as the small capacity of the transmission channel (available bandwidth), which is hard to manage and causes data acquisition delays. The seismic signals, in particular, after digitization, are compressed to make better use of the available channel. The use of a lossless compression algorithm causes variable efficiency that depends, generally, on the kind of signal to compress. We know that signals that change frequently in a time window, and that have a high RMS amplitude, are more difficult to compress with lossless compression, and hence need more bandwidth. Instead, signals with a low RMS amplitude and that change little in a time window, are better compressed with lossless compression and require smaller space channels. Various active volcanic phenomenology in eruption phases, could cause a big variation in some seismic signal parameters like RMS amplitude, this variation causes channel bandwidth consumption increase. This implies an efficiency evaluation of the Nanometrics® transmission protocol and compression algorithm used by the remote station instruments, especially in critical stages as when a volcano is preparing to erupt. Alternative protocols are proposed to increase the global evaluation quality of the Nanometrics® protocol and compression algorithm used by the RSP instrumentation. Comparisons between solutions are made by studying the relationship between seismic signal RMS amplitude and its bandwidth consumption. Studying the compression algorithm and researching potential optimization, helps build a plausible evaluation of the bandwidth needed in the critical stages that are typical in active volcanoes like Etna. Fri, 30 Jun 2006 22:00:00 GMT http://hdl.handle.net/2122/8359 2006-06-30T22:00:00Z http://hdl.handle.net/2122/8280 Title: A finite element Galerkin/least-squares method for computation of multicomponent compressible–incompressible flows Authors: Longo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Barsanti, M.; Dipartimento di Matematica Applicata, University of Pisa, Pisa, Italy; Cassioli, A.; Dipartimento di Sistemi e Informatica, University of Florence, Florence, Italy; Papale, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia Abstract: The space–time Galerkin/least-squares finite element method with discontinuity capturing (ST-GLSDC), developed by Hughes and collaborators [Shakib et al. A new finite element formulation for computational fluid dynamics: X. The compressible Euler and Navier–Stokes equations. Comput Methods Appl Mech Eng 1991;89:141–219], allows to study both compressible and incompressible single-fluid one-component flows. It is effective in the stabilization of the numerical solution without introducing excessive overdiffusion. In this work the development by Hauke and Hughes [A comparative study of different sets of variables for solving compressible and incompressible flows. Comput Methods Appl Mech Eng 1998;153:1–44] to pressure primitive variables is extended to single-fluid multicomponent compressible and incompressible flows of gas–liquid mixtures at local mechanical and chemical equilibrium. The stabilized algorithm is implemented in a parallel C++ library, which is tested on several benchmarks. The solution of the system of equations for the conservation of mass of each component, and of momentum and energy of the global mixture, requires the introduction of mass fractions as primitive variables to describe mixture composition. The weak formulation, the stabilization parameters, and the time-marching algorithm are rewritten in terms of the expanded set of variables, keeping similarity with the formulation in pressure variables. Wed, 29 Aug 2012 22:00:00 GMT http://hdl.handle.net/2122/8280 2012-08-29T22:00:00Z http://hdl.handle.net/2122/8278 Title: Sensitivity analysis for volcanic source modeling quality assessment and model selection Authors: Cannavo, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia Abstract: The increasing knowledge and understanding of volcanic sources has led to the development and implementation of sophisticated and complex mathematical models with the main goal of describing field and experimental data. Quantification of the model’s ability in describing the data becomes fundamental for a realistic estimate of the model parameters. The analysis of sensitivity can help us in identifying the parameters that significantly affect the model’s output and in assessing its quality factor. In this paper, we describe the Global Sensitivity Analysis (GSA) methods based both on Fourier Amplitude Sensitivity Test and on the Sobol’ approach and discuss their implementation in a Matlab software tool (GSAT). We also introduce a new criterion for model selection based on sensitivity analysis. The proposed approach is tested and applied to quantify the fitting ability of an analytic volcanic source model on a synthetic deformation data. Results show the validity of the method, against the traditional approaches, in supporting the volcanic model selection and the flexibility of the GSAT software tool in analyzing the model sensitivity. Sat, 31 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/8278 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8273 Title: High resolution finite volume central schemes for a compressibile two-phase model Authors: La Spina, G.; Dipartimento di Matematica L.Tonelli, University of Pisa, Italy; De' Michieli Vitturi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia Abstract: A modi_cation of the Kurganov, Noelle, Petrova central-upwind scheme [A. Kurganov et al., SIAM J. Sci. Comput., 23 (2001), pp. 707{740] for hyperbolic systems of conservation laws is presented. In this work, the numerical scheme is applied to a single-temperature model for compressible two-phase ow with pressure and velocity relaxations [E. Romenski et al., J. Sci. Comput., 42 (2010), pp. 68{95]. The system of governing equations of this model are expressed in conservative form, which is the necessary condition to use a central scheme. The numerical scheme presented is not based on the complete characteristic decomposition, but only on the information about the local speeds of propagation given by the maximum and minimum eigenvalue of the Jacobian of the uxes. We propose to use the numerical ux formulation of the central-upwind scheme in conjunction with a second-order reconstruction of the primitive variables and the MUSCL-Hancock method, where the boundary extrapolated values are evolved by half time step before the computation of the numerical uxes. To investigate the accuracy and robustness of the proposed scheme, two 1D Riemann-problems of an air/water mixture and a 2D shock-bubble-interaction problem are presented. Furthermore, a detailed comparison with the second order GFORCE scheme and the _rst order Lax-Friedrichs scheme is shown. To integrate the source terms an operator splitting approach is used and, under suitable conditions, it is shown that this integration can be computed analytically. Sat, 31 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/8273 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8094 Title: Segmentazione delle serie temporali nell’analisi dei dati: un esempio di applicazione a dati sismo-vulcanici. Authors: Montalto, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Aliotta, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Cannata, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Cassisi, C.; UNIVERSITÀ DEGLI STUDI DI CATANIA (Dipartimento di Matematica e Informatica) Abstract: Il presente report descrive quanto sviluppato dagli autori per l’analisi delle serie temporali utilizzate per il monitoraggio sismo-vulcanico del vulcano Etna. La necessità di ottenere una rappresentazione ridotta delle serie temporali ha portato alla ricerca ed alla implementazione degli algoritmi di segmentazione oggetto del presente lavoro. Le metodologie introdotte nel paragrafo 2, largamente applicate nella disciplina del data mining su serie temporali, costituiscono ad oggi lo stato dell’arte per quanto riguarda le tecniche di approssimazione di serie temporali. In particolare, l’applicazione dell’algoritmo bottom-up ha permesso una compressione elevata dei dati, consentendo quindi una rappresentazione con un numero di punti inferiore rispetto a quello delle serie temporali di partenza. In questo contesto la scelta delle soglie errore, legata indirettamente al numero di segmenti con cui si approssima la serie temporale, è stata scelta in modo empirico. Questa scelta è stata vincolata alla dimensione dei buffer di dati da impiegare per scopi di visualizzazione ed elaborazione. Future implementazioni riguarderanno l’ottimizzazione in linea degli algoritmi Sliding Window in modo da operare in real-time sugli streaming di dati ed ottimizzarne l’archiviazione e la visualizzazione. Sat, 31 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/8094 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8028 Title: Parallel ‘large’ dense matrix problems: application to 3D joint inversion of seismological and gravity data Authors: Tondi, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Cavazzoni, C.; CINECA, Interuniversity Computing Centre, Via Magnanelli 6/3, 40033 Casalecchio di Reno (BO), Italy; Danecek, P.; Univ Granada, Inst Andaluz Geofis, E-18071 Granada, Spain; Morelli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia Abstract: To obtain accurate and reliable estimations of the major lithological properties of the rock within a studied volume, geophysics uses the joint information provided by different geophysical datasets (e.g. gravimetric, magnetic, seismic). Representation of the different types of information entering the problem using probability density functions can provide the mathematical framework to formulate their combination. The maximum likelihood estimator of the resulting joint posterior probability density functions leads to the solution of the problem. However, one key problem appears to limit the use of this solver to an extensive range of real applications: information coming from potential fields that implies the presence of dense matrices in the resolving estimator. It is well known that dense matrix systems rapidly challenge both the algorithms and the computing platforms, and are not suited to high-resolution 3D geophysical analysis. In this study, we propose a procedure that allows us to obtain fast and reliable solutions of the joint posterior probability density functions in the presence of large gravity datasets and using sophisticated model parametrization. As it is particularly CPUconsuming, this 3D problem makes use of parallel computing to improve the performance and the accuracy of the simulations. Analysis of the correctness of the results, and the performance on different parallel environments, shows the portability and the efficiency of the code. This code is applied to a real experiment, where we succeed in recovering a 3D shear-wave velocity and density distribution within the upper mantle of the European continent, satisfying both the seismological and gravity data. On a multiprocessor machine, we have been able to handle forward and inverse calculations with a dense matrix of 215.66 Gb in 18 min, 20 s and 20 min, 54 s, respectively. Wed, 31 Oct 2012 23:00:00 GMT http://hdl.handle.net/2122/8028 2012-10-31T23:00:00Z http://hdl.handle.net/2122/7965 Title: A RESPER probe for measurements of RESistivity and PERmittivity Authors: Settimi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Editors: Beatrice besson; LAP LAMBERT Academic Publishing GmbH & Co. KG Heinrich-Böcking-Str. 6-8 66121; LAP LAMBERT Academic Publishing GmbH & Co. KG Heinrich-Böcking-Str. 6-8 66121; LAP LAMBERT Academic Publishing GmbH & Co. KG Heinrich-Böcking-Str. 6-8 66121; LAP LAMBERT Academic Publishing GmbH & Co. KG Heinrich-Böcking-Str. 6-8 66121, Saarbrücken, Germany Abstract: The electrical RESistivity and dielectric PERmittivity measuring device (RESPER) for non-invasive investigation of media is an exploiting electrical induction by means of capacitive coupling with media as terrestrial soils and concretes. The device utilizes a four-electrode probe to inject a radio frequency into a medium and register an induced current. Complex transfer impedance can be determined from a ratio between a potential measured across two electrodes, and an induced current flowing in the medium. Electrical parameters of resistivity and permittivity characterizing the medium can be established from the transfer impedance, using inversion formulas that also take into account the geometric ratio and position of the electrodes. The device exploits the in-phase and quadrature under sampling technique which, together with numerical operations performed by a microcontroller, allows the device to attain a required performance. It is possible to execute a number of numerical integrations which, combined with some circuit solutions, can reduce the amplitude and phase errors of the acquired signal. The device can operate at variable frequency, maintaining a suitable under-sampling frequency to fully exploit the analogical-digital acquisition performance both in velocity and dynamic range. Tue, 15 May 2012 22:00:00 GMT http://hdl.handle.net/2122/7965 2012-05-15T22:00:00Z