http://hdl.handle.net/2122/213 Fri, 24 May 2013 02:20:06 GMT 2013-05-24T02:20:06Z http://hdl.handle.net/2122/8658 Title: The Earth Expansion Evidence – A Challenge for Geology, Geophysics and Astronomy Authors: Scalera, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Boschi, E.; University of Bologna; Cwojdzinski, S.; Polish Geological Survey Editors: Scalera, Giancarlo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Boschi, Enzo; University of Bologna; Cwojdzinski, Stefan; Polish Geological Survey Fri, 30 Nov 2012 23:00:00 GMT http://hdl.handle.net/2122/8658 2012-11-30T23:00:00Z http://hdl.handle.net/2122/8657 Title: Geodetic Problems of an Expanding Globe - Simple Critical Arguments Authors: Scalera, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Editors: Scalera, Giancarlo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Boschi, Enzo; University of Bologna; Cwojdzinski, Stefan; Polish Geological Survey Abstract: Because unequivocal evidence exist in favor of the expansion of the globe through geologic time, and if the expansion of our planetary body is ongoing today and not confined to the past or episodic in time, some subtle causes must consequently exist of the inability of Geodesy in revealing a plausible expansion rate. Old critical arguments around the possibility of a vicious circle in the geodetic theoretical methods (Blinov, 1987; Scalera, 2003) has revealed their inadequacy in respect of the geometry of space geodesy. On the bases of an old argument (Scalera, 2003), it has been then developed a new more realistic one, in which it is demonstrated that spurious effects can probably bias what is believed to be systematic-error-free data. It is argued that Geodesy still has to full develop a theoretical treatment of an expanding globe Fri, 30 Nov 2012 23:00:00 GMT http://hdl.handle.net/2122/8657 2012-11-30T23:00:00Z http://hdl.handle.net/2122/8209 Title: The April 3, 2010 earthquake along the Pernicana fault (Mt. Etna - Italy): analysis of satellite and in situ ground deformation data integrated by the SISTEM approach Authors: Guglielmino, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Bonforte, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Puglisi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Bignami, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Stramondo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Obrizzo, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Wegmuller, U.; GAMMA Remote Sensing, CH-3073 Gümligen, Switzerland; Briole, P.; Ecole Normale Supérieure, Laboratoire de Géologie, UMR-CNRS 8538, 24 Rue Lhomond, 75005 Paris Abstract: Etna is worldwide known as one of the most studied and monitored active volcanoes. Flank instability along the eastern and southern portion of Mt. Etna has been observed and measured thanks to geodetic networks and InSAR data analysis. The spreading area is bordered to the north by the east-west Pernicana Fault System (PFS) which dynamic is often linked with the eruptive activity, as recently observed during the 2002-2003 eruption. A seismic sequence occurred since April 2-3, 2010, along the PFS with two very shallow (a few hundred meters) mainshocks of magnitude 3.6 and 3.5. Explosions and ash emissions at the summit craters followed this swarm and culminated some days later (April 7-8). Just after the earthquake, specific GPS surveys were carried out aimed at monitoring the eastern part of the Pernicana fault, and the leveling route on the northeastern flank of the volcano was also surveyed. Trying to investigate the deformation occurred along the PFS during the events of April 3rd 2010, we performed a DInSAR (Differential Interferometric Synthetic Aperture Radar) analysis of ascending and descending Envisat, and of ascending ALOS-PALSAR images encompassing the date of the earthquake. The Envisat interferograms show very intense but local deformation on the Envisat ascending data and a low signal for the descending geometry, close to the Pernicana fault trace. This is probably due to the oblique normal/leftlateral kinematics of the PFS (as deduced also by GPS and leveling data), indeed both vertical (lowering) and horizontal (eastwards) components of motion produce a strong stretching of the LOS (Line Of Sight) distance for ascending geometry, while the two components act in opposite ways for the descending geometry, resulting in lower LOS distance variations compared to the ascending data set. We analyzed also the ALOS pair referring to 21/02/2010 – 08/04/2010 time and acquired along the ascending track number 638. The ALOS interferogram clearly show three fringes corresponding to roughly 35 cm of LOS displacement. The preliminary modeling of the interferograms agree with the seismic information (very shallow faulting, seismic moment) and show that the medium behave elastically. In order to investigate the ground deformation pattern associated with this event, an application of the novel SISTEM (Simultaneous and Integrated Strain Tensor Estimation from geodetic and satellite deformation Measurements) approach is presented here. To achieve higher accuracy and get better constraint of the 3D components of the displacements, we improved the standard formulation of SISTEM approach, based on the GPS and a single DInSAR sensor, in order to take into account all the available dataset (GPS, leveling, ascending and descending ENVISAT C-Band interferograms and the ALOS L-Band data). The 3D displacement maps obtained using the SISTEM approach well show the kinematics of the PFS, and are able to reconstruct also the ground deformation affecting the whole investigated area, defining the movements of the north-eastern flank of the volcano. These results, which provide an accurate spatial characterization of ground deformation, are hence promising for future studies aimed at improving the knowledge about the kinematics of the active faults of Mt. Etna. Thu, 31 Mar 2011 22:00:00 GMT http://hdl.handle.net/2122/8209 2011-03-31T22:00:00Z http://hdl.handle.net/2122/7946 Title: GPS Permanent Network Solution: the Impact of Temporal Correlations Authors: Barzaghi, R.; Politecnico di Milano; Borghi, A.; Politecnico di Milano; Crespi, M.; Università La Sapienza; Pietrantonio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Riguzzi, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia Abstract: . In this work we analysed the time series of daily solutions of 4 Italian GPS permanent stations with the aim of investigating the presence of temporal correlations and their impact on the estimation of weekly solution and velocity field precisions. We found that precisions are remarkably lower when temporal correlations are considered; in particular, the mean horizontal precisions of weekly solutions are up to 5 times lower and the horizontal velocity precisions are about 1.5-2 times lower. This topic has 2 relevant applications: the assessment of the quality of a reference system maintenance by GPS permanent stations and the coordinate differences significance test for geodynamical applications. Wed, 31 Dec 2003 23:00:00 GMT http://hdl.handle.net/2122/7946 2003-12-31T23:00:00Z http://hdl.handle.net/2122/7745 Title: Distensional Mediterranean and World Orogens – Their Possible Bearing to Mega-Dikes' Active Rising Authors: Scalera, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Editors: Scalera, Giancarlo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Cwojdzinski, Stefan; Polish Geological Survey Abstract: (extended abstract) Mon, 03 Oct 2011 22:00:00 GMT http://hdl.handle.net/2122/7745 2011-10-03T22:00:00Z http://hdl.handle.net/2122/7288 Title: Imaging the multi‐level magma reservoir at Mt. Etna volcano (Italy) Authors: Aloisi, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Mattia, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Ferlito, C.; Dipartimento di Geologia, Università degli Studi di Catania; Palano, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Bruno, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Cannavò, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia Abstract: The continuous GPS network operating on Mt. Etna with its 36 stations is currently one of the largest worldwide. The aim of this network is the evaluation of volcanic hazard and the modelling of the active sources. In this paper, we propose an in‐depth analysis and modelling of continuous GPS data collected at Mt. Etna from May 2008 to December 2010. The analyzed period has been divided into four different coherent phases: 1) 14 May 2008–02 August 2008 (deflation of the entire GPS network); 2) 02 August 2008–14 June 2009 (deflation of the summit area and inflation at lower heights); 3) 14 June 2009–21 May 2010 (inflation of the entire GPS network); 4) 21 May 2010–31 December 2010 (inflation at medium and low heights and end of the inflation in the summit area). Analytical models indicate a non-uniform deformation style revealing spaced sources acting at different time on different segments of a multi-level magma reservoir. The Etnean plumbing system imaged here is depicted as an elongated magma reservoir that extends from the volcano body downwards to about 6.5 km below sea level (b.s.l.), sloping slightly towards the North-West, with storage volumes located at about 6.5, 2.0 and 0.0 km (b.s.l.). The changes in position of the modelled pressure sources during the analyzed time intervals indicate that, throughout the 2008 eruptive period, the deformation field was mostly driven by the upward migration of magma. On the other hand, the pattern of deformation recorded after the end of the eruption strongly suggests a significant contribution of the magma overpressure generated by the gas boiling, thus outlining the importance of volatiles content in magma. Fri, 19 Aug 2011 22:00:00 GMT http://hdl.handle.net/2122/7288 2011-08-19T22:00:00Z http://hdl.handle.net/2122/6813 Title: Stochastic modelling considering ionospheric scintillation effects on GNSS relative and point positioning Authors: Alves da Silva, H.; Department of Cartography, Sao Paulo State University, Roberto Simonsen – 305, Presidente Prudente, SP, 19060-900, Brazil; Camargo, P.; Department of Cartography, Sao Paulo State University, Roberto Simonsen – 305, Presidente Prudente, SP, 19060-900, Brazil; Galera Monico, J. F.; Department of Cartography, Sao Paulo State University, Roberto Simonsen – 305, Presidente Prudente, SP, 19060-900, Brazil; Aquino, M.; Institute of Engineering Surveying and Space Geodesy (IESSG), University of Nottingham, University Park, Nottingham NG7 2RD, UK; Marques, H. A.; Department of Cartography, Sao Paulo State University, Roberto Simonsen – 305, Presidente Prudente, SP, 19060-900, Brazil; De Franceschi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Dodson, A.; Institute of Engineering Surveying and Space Geodesy (IESSG), University of Nottingham, University Park, Nottingham NG7 2RD, UK Abstract: Global Navigation Satellite Systems (GNSS), in particular the Global Positioning System (GPS), have been widely used for high accuracy geodetic positioning. The Least Squares functional models related to the GNSS observables have been more extensively studied than the corresponding stochastic models, given that the development of the latter is significantly more complex. As a result, a simplified stochastic model is often used in GNSS positioning, which assumes that all the GNSS observables are statistically independent and of the same quality, i.e. a similar variance is assigned indiscriminately to all of the measurements. However, the definition of the stochastic model may be approached from a more detailed perspective, considering specific effects affecting each observable individually, as for example the effects of ionospheric scintillation. These effects relate to phase and amplitude fluctuations in the satellites signals that occur due to diffraction on electron density irregularities in the ionosphere and are particularly relevant at equatorial and high latitude regions, especially during periods of high solar activity. As a consequence, degraded measurement quality and poorer positioning accuracy may result. This paper takes advantage of the availability of specially designed GNSS receivers that provide parameters indicating the level of phase and amplitude scintillation on the signals, which therefore can be used to mitigate these effects through suitable improvements in the least squares stochastic model. The stochastic model considering ionospheric scintillation effects has been implemented following the approach described in Aquino et al. (2009), which is based on the computation of weights derived from the scintillation sensitive receiver tacking models of Conker et al. (2003). The methodology and algorithms to account for these effects in the stochastic model are described and results of experiments where GPS data were processed in both a relative and a point positioning mode are presented and discussed. Two programs have been developed to enable the analyses: GPSeq (currently under development at the FCT/UNESP Sao Paulo State University – Brazil) and PP_Sc (developed in a collaborative project between FCT/UNESP and Nottingham University – UK). The point positioning approach is based on an epoch by epoch solution, whereas the relative positioning on an accumulated solution using a Kalman Filter and the LAMBDA method to solve the Double Differences ambiguities. Additionally to the use of an improved stochastic model, all data processing in this paper were performed using an option implemented in both programs, to estimate, for each observable, an individual ionospheric parameter modelled as a stochastic process, using either the white noise or the random walk correlation models. Data from a network of GPS Ionospheric Scintillation and TEC Monitor (GISTM) receivers set up in Northern Europe as part of the ISACCO project (De Franceschi et al., 2006) were used in the experiments. The point positioning results have shown improvements of the order of 45% in height accuracy when the proposed stochastic model is applied. In the static relative positioning, improvements of the order of 50%, also in height accuracy, have been reached under moderate to strong scintillation conditions. These and further results are discussed in this paper. Sun, 02 May 2010 22:00:00 GMT http://hdl.handle.net/2122/6813 2010-05-02T22:00:00Z http://hdl.handle.net/2122/6730 Title: Modelling of InSAR (LOS) changes by means of 3D extended pressured bodies with free geometry. Application to Campi Flegrei. Authors: Camacho, A.G; Inst. Astronomia y Geodesia (CSIC-UCM), Madrid; Fernandez, J.; Inst. Astronomia y Geodesia (CSIC-UCM), Madrid; Gonzalez, P.J.; Inst. Astronomia y Geodesia (CSIC-UCM), Madrid; Berrino, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia Abstract: InSAR measures can provide information about changes in distance between the ground and the satellite in radar line-of-sight (LOS) direction. Sometimes, as in the case of volcanic activity, the corresponding ground deformations can be modeled by means of pressure and/or mass sources. Usually, point sources and regular prolate or oblate bodies are used as source geometry for deformation. In this communication, we show a new method for non-linear inversion of position and gravity changes as produced by extended bodies with a free geometry. Their structures are described as aggregation of elemental sources with anomalous density and pressure, and they are modeled to fit the whole data and to keep some regularity conditions. A growth process permits to build general geometrical configurations. The method is tested by application to data of gravity and InSAR (LOS data for ascending and descending orbits) for the volcanic area of Campi Flegrei (Italy). Results are drawn with respect a structural gravimetric model and compared with previous models. Thu, 31 Dec 2009 23:00:00 GMT http://hdl.handle.net/2122/6730 2009-12-31T23:00:00Z http://hdl.handle.net/2122/6728 Title: Geometrical and physical properties of the 1982-84 deformation source at Campi Flegrei - Italy Authors: Bonafede, M.; Department of Physics, Section of Geophysics, University of Bologna, Italy; Trasatti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Giunchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Berrino, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia Abstract: Deformation of the ground surface in volcanic areas is generally recognized as a reliable indicator of unrest, possibly resulting from the intrusion of fresh magma within the shallow rock layers. The intrusion process is usually represented by a deformation source such as an ellipsoidal pressurized cavity, embedded within a homogeneous and elastic half-space. Similar source models allow inferring the depth, the location and the (incremental) volume of the intrusion, which are very important parameters for volcanic risk implications. However, assuming a homogeneous and elastic rheology and, assigning a priori the shape and the mechanism of the source (within a very restricted “library” of available solutions) may bias considerably the inference of source parameters. In complete generality, any point source deformation, including overpressure sources, may be described in terms of a suitable moment tensor, while the assumption of an overpressure source strongly restricts the variety of allowable moment tensors. In particular, by assuming a pressurized cavity, we rule out the possibility that either shear failure may precede magma emplacement (seismically induced intrusion) or may accompany it (mixed tensile and shear mode fracture). Another possibility is that a pre-existent weakness plane may be chosen by the ascending magma (fracture toughness heterogeneity). We perform joint inversion of levelling and EDM data (part of latter are unpublished), collected during the 1982-84 unrest at Campi Flegrei caldera: a 43% misfit reduction is obtained for a general moment source if the elastic heterogeneities computed from seismic tomography are accouted for. The inferred source is at 5.2 km depth but cannot be interpreted as a simple pressurized cavity. Moreover, if mass conservation is accounted for, magma emplaced within a shallow source must come from a (generally deeper) reservoir, which is usually assumed to be deep enough to be simply neglected. At Campi Flegrei, seismic tomography indicates that the “deep” magma source is rather shallow (at 7-8 km depth), so that its presence should be included in any thorough attempt to source modeling. Taking into account a deflating source at 7.5 km depth (represented either as a horizontal sill or as an isotropic cavity) and an inflating moment source, the fit of both levelling and EDM data improves further (misfit reduction 80%), but still the best fitting moment source (at 5.5 km depth) falls outside the range of pressurized ellipsoidal cavities. The shallow moment source may be decomposed in a tensile and a shear dislocation. No clue is obtained that the shear and the tensile mechanisms should be located in different positions. Our favourite interpretation is in terms of a crack opening in mixed tensile and shear mode, as would be provided by fluid magma unwelding pre-stressed solid rock. Although this decomposition of the source is not unique, the proposed solution is physically motivated by the minimum overpressure requirement. An important implication of this new interpretation is that the magma emplaced in the shallow moment source during the 1982-84 unrest was not added to already resident magma at the same position. Thu, 31 Dec 2009 23:00:00 GMT http://hdl.handle.net/2122/6728 2009-12-31T23:00:00Z http://hdl.handle.net/2122/6317 Title: The 2010 Chile Earthquake: Rapid Assessments of Tsunami Authors: Michelini, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Lauciani, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Selvaggi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Lomax, A.; ALomax Scientific Abstract: After an earthquake underwater, rapid real-time assessment of earthquake parameters is important for emergency response related to infrastructure damage and, perhaps more exigently, for issuing warnings of the possibility of an impending tsunami. Since 2005, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) has worked on the rapid quantification of earthquake magnitude and tsunami potential, especially for the Mediterranean area. This work includes quantification of earthquake size from standard moment tensor inversion, quantification of earthquake size and tsunamigenic potential using P waveforms, and calculation of an archive of readily accessible tsunami scenarios. Mon, 30 Aug 2010 22:00:00 GMT http://hdl.handle.net/2122/6317 2010-08-30T22:00:00Z