http://hdl.handle.net/2122/203 2013-05-23T08:22:08Z http://hdl.handle.net/2122/8685 Title: Studio di fattibilità per il monitoraggio delle deformazioni del fondo marino tramite GPS su una meda elastica (Golfo di Pozzuoli – Campi Flegrei) Authors: De Martino, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Guardato, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Tammaro, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Iannaccone, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia Abstract: The continuous measurement of ground deformations is an important contribution to the monitoring of volcanic areas. When the volcano is totally or partially submerged, the traditional geodetic methods cannot be applied and the measures of seafloor deformation are extremely difficult and expensive. This paper describes the installation of a continuous GPS station on an elastic beacon. The measurements were conducted in the Campi Flegrei Caldera (Gulf of Pozzuoli, Naples), whose vertical displacements are related to the bradyseismic phenomenon. Experimental observations show that it’s possible to monitor vertical displacement of seafloor with a resolution of a few centimeters, also taking into account for measurement errors (due to weather and sea conditions acting on the elastic beacon). This non expensive technique is relevant at Campi Flegrei area, because it extends the ground deformation monitoring at sea, contributing to a better modeling of the deformation field. 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8648 Title: Understanding earthquakes: The key role of radar images Authors: Atzori, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia Abstract: The investigation of the fault rupture underlying earthquakes greatly improved thanks to the spread of radar images. Following pioneer applications in the eighties, Interferometry from Synthetic Aperture Radar (InSAR) gained a prominent role in geodesy. Its capability to measure millimetric deformations for wide areas and the increased data availability from the early nineties, made InSAR a diffused and accepted analysis tool in tectonics, though several factors contribute to reduce the data quality. With the introduction of analytical or numerical modeling, InSAR maps are used to infer the source of an earthquake by means of data inversion. Newly developed algorithms, known as InSAR time-series, allowed to further improve the data accuracy and completeness, strengthening the InSAR contribution even in the study of the inter- and post-seismic phase. In this work we describe the rationale at the base of the whole processing, showing its application to the New Zealand 2010-2011 seismic sequence. 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8499 Title: Geological and geophysical investigation of Kamil crater, Egypt Authors: Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Nicolosi, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zeoli, A.; Museo Nazionale dell’Antartide Universita` di Siena, Via Laterina 8, 53100 Siena, Italy; El Khrepy, S.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt; Lethy, A.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt; Hafez, M.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt; El Gabry, M.; National Research Institute of Astronomy and Geophysics, Helwan, Egypt; El Barkooky, A.; Department of Geology, Faculty of Sciences, Cairo University, Giza, Egypt; Barakat, A.; Egyptian Mineral Resources Authority, 3 Salah Salem Road, Abassiya, Cairo, Egypt; Gomaa, M.; Museo Nazionale dell’Antartide Universita` di Siena, Via Laterina 8, 53100 Siena, Italy; Radwan, A. M.; Museo Nazionale dell’Antartide Universita` di Siena, Via Laterina 8, 53100 Siena, Italy; El Sharkawi, M.; Department of Geology, Faculty of Sciences, Cairo University, Giza, Egypt; D’Orazio, M.; Dipartimento di Scienze della Terra, Universita` di Pisa, Via S. Maria 53, 56126 Pisa, Italy; Folco, L.; Dipartimento di Scienze della Terra, Universita` di Pisa, Via S. Maria 53, 56126 Pisa, Italy Abstract: We detail the Kamil crater (Egypt) structure and refine the impact scenario, based on the geological and geophysical data collected during our first expedition in February 2010. Kamil Crater is a model for terrestrial small-scale hypervelocity impact craters. It is an exceptionally well-preserved, simple crater with a diameter of 45 m, depth of 10 m, and rayed pattern of bright ejecta. It occurs in a simple geological context: flat, rocky desert surface, and target rocks comprising subhorizontally layered sandstones. The high depth-to-diameter ratio of the transient crater, its concave, yet asymmetric, bottom, and the fact that Kamil Crater is not part of a crater field confirm that it formed by the impact of a single iron mass (or a tight cluster of fragments) that fragmented upon hypervelocity impact with the ground. The circular crater shape and asymmetries in ejecta and shrapnel distributions coherently indicate a direction of incidence from the NW and an impact angle of approximately 30 to 45 . Newly identified asymmetries, including the off-center bottom of the transient crater floor downrange, maximum overturning of target rocks along the impact direction, and lower crater rim elevation downrange, may be diagnostic of oblique impacts in well-preserved craters. Geomagnetic data reveal no buried individual impactor masses >100 kg and suggest that the total mass of the buried shrapnel >100 g is approximately 1050–1700 kg. Based on this mass value plus that of shrapnel >10 g identified earlier on the surface during systematic search, the new estimate of the minimum projectile mass is approximately 5 t. 2012-12-13T23:00:00Z http://hdl.handle.net/2122/8401 Title: Automatic detection of landslides at Stromboli using neural network analysis of seismic signals Authors: D'Auria, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Esposito, A.; 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; 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 Abstract: Landslides along the Sciara del Fuoco flank of Stromboli volcano are generally accompanied by c1istinctive seismic signals which can be used for srudying this phenomenon. These signals are characterìzed by a spectral content with higher frequencies and a wider band than the typical explosion quakes and volcanic tremor signals which are continuously recorded at Stromboli. Furthermore their amplirude envelope usually shows a cigar-like shape. These two fearures make the detection of such signals quite easy. The detection of landslides at Stromboli has shown to be an important shortterm precursor of effusive eruptions. Before the Feb. 27th 2007 eruption, the opening of the effusive vents was preceded by few hours oI increased occurrence of landslide signals (Martini et al., 2007). Furthermore since the Sciara del Fuoco has shown significant instabilities during the 2002-2003 eruption, the automatic detection of landslide signals is an important monitoring tool for notifying variations in the stability of this flank. We propose a technique based on a Multi Layer Perceptron (MLP) neural network which has shown excellent performances. The network is composed of two layer of neurons, the hidden and the output. The hidden layer is composed of 4 neurons while the output layer is composed by a single neuron whose output value ranges between Oand 1, with values higher than a given threshold (e.g. 0.5) meaning positive detection. The continuous seismic signals are analysed using moving windows of 24 s, with an overlap of 12 s. For each of these windows the neural output is computed. The waveforms of each time window are parametrized using both their spectrogram and their amplirude envelope. The spectrogram is described using the Linear Preclictive Cocling (L'PC) technique which allows to represent the spectral content using a limited number of coefficients. The whole signal is c1ivided into 8 sub-windows of 5.12 s length, with an overlapping of 2.56 s. For each sub-window we compute 6 LPC coefficients, so each spectrogram is described by only 48 coefficients. The amplirude envelope is defined by computing the c1ifference between the maximum and minimum value over 1 s sub-windows obtaining 24 coefficients. In conclusion we use an input vector composed of 72 elements (48+24). This vector has shown to be an efficient and compact representation of the raw signal (composed of 1200 samples) (Esposito et al. 2006). The dataset used for determining the network parameters is composed of 537 signals, c1ivided in two classes: 267 landslide signals and 270 other signals (explosions and tremor). The classification of these signals has been performed by analysts. The training is carried out using subsets of 5/8 of the total dataset. The testing subsets are composed by the remaining 3/8. The network has shown a performance of about 98.7%. This value is an average over 6 random permutations of the dataset. A preliminary real-rime automatic system has already been implemented. This system performs continuous analysis of the seismic signals, publishing them on internal web pages. It allows a detection of the landslides and a comparison with the past activity on arbitrary rime intervals. 2009-05-31T22:00:00Z http://hdl.handle.net/2122/8021 Title: Procedura automatica per il calcolo delle ShakeMaps e rilocalizzazione degli eventi presso la sede di Ancona dell'INGV-CNT Authors: D'Alema, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Carannante, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia 2012-03-31T22:00:00Z http://hdl.handle.net/2122/7970 Title: crustal fracturing field and presence of fluid as revealed by seismic anisotropy: case-histories from seismogenic areas in the Apennines Authors: Pastori, Marina; Università degli studi di Perugia Abstract: During the last decades, the study of seismic anisotropy has provided useful information for the interpretation and evaluation of the stress field and active crustal deformation. Seismic anisotropy can yield valuable information on upper crustal structure, fracture field, and presence of fluid-saturated rocks crossed by shear waves. Several studies worldwide demonstrate that seismic anisotropy is related to stress-aligned, filled-fluid micro-cracks (EDA model, Crampin et al., 1984b; Crampin, 1993). The seismic anisotropy is an almost ubiquitous property of the Earth and the Shear Wave Splitting is the most unambiguous indicator of anisotropy, but the automatic estimation of the splitting parameters is difficult because the effect of the anisotropy on a seismogram is a second order, not easily detectable effect. Different researchers developed automated techniques aimed to study the Shear Wave Splitting: in this study, the results of different codes are compared in order to evaluate the best method for automatic anisotropy evaluation. In the last three years, an automatic analysis code, “Anisomat+”, was developed, tested and improved to calculate the anisotropic parameters: fast polarization direction () and delay time (∂t). “Anisomat+” consists of a set of MatLab scripts able to retrieve automatically crustal anisotropy parameters from three-component seismic recordings of local earthquakes. It needs waveforms and hypocentral parameters in the format routinely archived by the Istituto Nazionale di Geofisica e Vulcanologia (INGV). The code uses horizontal component cross-correlation method: a mathematical algorithm aimed to measure the similarity of the pulse shape between two shear waves. Anisomat+ has been compared to other two automatic analysis codes (SPY and SHEBA) and tested on three zones of the Apennines (Val d’Agri, Tiber Valley and L’Aquila surroundings). It was observed that, if the number of measures is large enough, at each station the average values of the parameters (fast direction and delay time) are comparable. The main goal in developing of an automatic code was to have tool able to work on a big amount of data, in a short time, by reducing the errors due to the subjectivity. These two acquirements are very useful and are the basis to develop a quasi real-time monitoring of the anisotropic parameters. The anisotropic parameters, resulting from the automatic computation, have been interpreted to determine the fracture field geometries; for each area, I defined the dominant fast direction and the intensity of the anisotropy, interpreting these results in the light of the geological and structural setting and of two anisotropic interpretative models, proposed in the literature. In the first one, proposed by Zinke and Zoback (2000), the local stress field and cracks are aligned by tectonics phases and are not necessarily related to the presently active stress field. Therefore the anisotropic parameters variations are only space-dependent. In the second, EDA model (Crampin, 1993), and its development in the APE model (Zatsepin and Crampin, 1995) fluid-filled micro-cracks are aligned or ‘opened’ by the active stress field and the variation of the stress field might be related to the evolution of the pore pressure in time; therefore in this case the variation of the anisotropic parameters are both space- and time- dependent. I recognized that the average of fast directions, in the three selected areas, are oriented NW-SE, in agreement with the orientation of the active stress field, as suggested by the EDA model, proposed by Crampin (1993), but also, by the proposed by Zinke and Zoback model; in fact, NW-SE direction corresponds also to the strike of the main fault structures in the three study regions. The mean values of the magnitude of the normalized delay time range from 0.005 s/km to 0.007 s/km and to 0.009 s/km, respectively for the L'Aquila (AQU) area, the High Tiber Valley (ATF) and the Val d'Agri (VA), suggesting a 3-4% of crustal anisotropy (Piccinini et al., 2006). In each area are also examined the spatial and temporal distribution of anisotropic parameters, which lead to some innovative observations, listed below. o The higher values of normalized delay times have been observed in those zones where most of the seismic events occur. This aspect was further investigated, by evaluating the average seismic rate, in a time period, between years 2005 and 2010, longer than the lapse of time, analyzed in the anisotropic studies. This comparison has highlighted that the value of the normalised delay time is larger where the seismicity rate is higher. o In the Alto Tiberina Fault area the higher values of normalised delay time are not only related to the presence of a high seismicity rate but also to the presence of a tectonically doubled carbonate succession. Therefore, also the lithology, plays a important role in hosting and preserving the micro-fracture network responsible for the anisotropic field. o The observed temporal variations of anisotropic parameters, have been observed and related to the fluctuation of pore fluid pressure at depth possibly induced by different mechanisms in the different regions, for instance, changes in the water table level in Val D’Agri (Valoroso et al., GJI submitted), occurrence of the April 6th Mw=6.1 earthquake in L’Aquila (Lucente et al., 2010). Since these variations have been recognized, it is possible to affirm that the models that better fit my results, both in term of fast directions and of delay times, seems to be those proposed by Crampin (1993) and Zatsepin & Crampin (1995), respectively EDA and APE models. 2011-02-16T23:00:00Z 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. 2012-05-15T22:00:00Z http://hdl.handle.net/2122/7888 Title: Downhole Measurements in the AND-2A Borehole, ANDRILL Southern McMurdo Sound Project, Antarctica Authors: Wonik, T.; Leibniz Institute for Applied Geophysics, 30655 Hannover - Germany; Grelle, T.; Leibniz Institute for Applied Geophysics, 30655 Hannover - Germany; Handwerger, D.; TerraTek (Schlumberger), Salt Lake City, UT 84104 - USA; Jarrard, R. D.; Dept. of Geology and Geophysics, Univ. of Utah, Salt Lake City, UT 84112 - USA; McKee, A.; Raytheon Polar Services Corporation, Centennial, CO 80112-3938 - USA; Patterson, T.; Montana Tech, 1300 West Park Street, Butte, MT 59701 - USA; Paulsen, T.; Dept. of Geology, Univ. of Wisconsin at Oshkosh, Oshkosh, WI 54901-8649 - USA; Pierdominici, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Schmitt, D. R.; Inst. for Geophysical Research, Dept. of Physics, Univ. of Alberta, Edmonton, Alberta, T6G 2G7 - Canada; Schröder, H.; Leibniz Institute for Applied Geophysics, 30655 Hannover - Germany; Speece, M.; Montana Tech, 1300 West Park Street, Butte, MT 59701 - USA; Wilson, T.; School of Earth Sciences, The Ohio State University, Columbus, OH 43210-1522 - USA; the ANDRIL-SMS Science Team; http://andrill.org/projects/sms/team.html Abstract: Under the framework of the ANDRILL Southern McMurdo Sound (SMS) Project successful downhole experiments were conducted in the 1138.54 metre (m)-deep AND-2A borehole. Wireline logs successfully recorded were: magnetic susceptibility, spectral gamma ray, sonic velocity, borehole televiewer, neutron porosity, density, calliper, geochemistry, temperature and dipmeter. A resistivity tool and its backup both failed to operate, thus resistivity data were not collected. Due to hole conditions, logs were collected in several passes from the total depth at ~1138 metres below sea floor (mbsf) to ~230 mbsf, except for some intervals that were either inaccessible due to bridging or were shielded by the drill string. Furthermore, a Vertical Seismic Profile (VSP) was created from ~1000 mbsf up to the sea floor. The first hydraulic fracturing stress measurements in Antarctica were conducted in the interval 1000-1138 mbsf. This extensive data set will allow the SMS Science Team to reach some of the ambitious objectives of the SMS Project. Valuable contributions can be expected for the following topics: cyclicity and climate change, heat flux and fluid flow, seismic stratigraphy in the Victoria Land Basin, and structure and state of the modern crustal stress field. 2008-12-31T23:00:00Z http://hdl.handle.net/2122/7805 Title: Volcanic Ash Cloud Properties: Comparison Between MODIS Satellite Retrievals and FALL3D Transport Model Authors: Corradini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Merucci, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Folch, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia Abstract: The moderate Resolution Imaging Spectroradiometer (MODIS) is a multispectral satellite instrument operating from the visible to thermal infrared spectral range. FALL3D is a 3-D time-dependent Eulerian model for the transport and deposition of volcanic particles. In this letter, quantitative comparison between the volcanic cloud ash mass and optical depth retrieved by MODIS and modeled by FALL3D has been performed. Three MODIS images collected on October 28, 29, and 30 on Mt. Etna volcano during the 2002 eruption have been considered as test cases. The results show a general good agreement between the retrieved and the modeled volcanic clouds in the first 300 km from the vents. Even if the modeled volcanic cloud area is systematically wider than the retrieved area, the ash total mass is comparable and varies between 35 and 60 kt and between 20 and 42 kt for FALL3D and MODIS, respectively. The mean aerosol optical depth (AOD) values are in good agreement and approximately equal to 0.8. When the whole volcanic clouds are considered the ash areas, then the total ash masses, computed by FALL3D model, are significantly greater than the same parameters retrieved from the MODIS data, while the mean AOD values remain in very good agreement and equal to about 0.6. The volcanic cloud direction in its distal part is not coincident for the October 29 and 30, 2002 images due to the difference between the real and the modeled local wind fields. Finally, the MODIS maps show regions of high mass and AOD due to volcanic puffs not modeled by FALL3D. 2010-12-31T23:00:00Z http://hdl.handle.net/2122/7752 Title: Redesign of an auto-levelling base for submarine seismic sensor Authors: D'Anna, Marco; Università degli Studi di Palermo; Ingrassia, Tommaso; Università degli Studi di Palermo; Mangano, Giorgio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Nigrelli, Vincenzo; Università degli Studi di Palermo Abstract: The OBS (acronym of Ocean Bottom Seismometer) is a system to monitor the submarine seismic activity. To properly work, an OBS system needs a suitable auto-levelling base to maintain a fixed (horizontal) position during the measurement phases. In this work a new auto-levelling base for submarine seismic sensors has been designed. During the redesign process a preliminary phase of analysis of the state of art has been made. Afterwards, the technological solutions chosen by different manufactures have been critically analysed, and a full description of their functionalities, working principles and system performances has been carried out. Later, some innovative concepts have been proposed. Among these ones, the most interesting are the auto-levelling bases with spherical joint, based on: air bearings, ball bearings and magnetic levitation systems. The concept scoring method has been used to identify. as best concept, the auto-levelling base with spherical joint and air bearings system. Successively, the chosen concept has been implemented: the technical working principles have been studied to choose the best solutions in terms of dimensions, shapes, materials of all base components. A full parametric CAD model of the auto-levelling base has been also created. The new designed base, by using a very innovative auto-levelling system, allows to obtain very good results as regards the accuracy of positioning, so ensuring a remarkable improvement of the performances of the ocean bottom seismometers. 2011-06-14T22:00:00Z