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Ferretti, Alessandro
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Ferretti, Alessandro
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- PublicationOpen AccessInterseismic Strain Accumulation in the Gargano Promontory (Central Italy)(2007-04-15)
; ; ; ; ; ; ; ;Atzori, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Hunstad, I.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Tolomei, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Salvi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Brunori, C. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Ferretti, A.; Tele Rilevamento Europa, s.r.l., Milano, Italy ;Cespa, S.; Tele Rilevamento Europa, s.r.l., Milano, Italy; ; ; ; ; ;The Gargano promontory is a ENE-WSW topographical and structural high located at the inner border of the Apulia foreland. The post-Miocene tectonics of the Gargano area is characterized mainly by E-W strike-slip and NW-SE normal faults, whose present state of activity is debated, since there have been no large earthquakes in the instrumental era. Still, the Gargano is well known as a seismically active zone: destructive earthquakes (and even a tsunami) have occurred in historical times, with felt effects up to XI MCS, although the exact location of the seismogenic sources is uncertain. The level of background seismicity is low, with a maximum magnitude Mw=5.4 occurring in the central part of the promontory. We have investigated the surface deformation in the area using the PS-InSAR processing technique. We have analysed 83 descending, and 31 ascending images, obtaining good coherence over about 200.000 Permanent Scatterers. We have modeled the ground velocity field using elastic dislocation models and a non-linear inversion scheme. The modeling preliminary results suggest that the area is presently accumulating strain along the E-W Mattinata fault, with locking depths in the range 10 to 15 km207 2164 - PublicationRestrictedCoseismic deformation pattern of the Emilia 2012 seismic sequence imaged by Radarsat-1 interferometry(2012-10)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Bignami, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Burrato, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Cannelli, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Chini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Falcucci, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Ferretti, A.; Tele-Rilevamento Europa s.r.l. ;Gori, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Kyriakopoulos, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Melini, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Moro, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Novali, F.; Tele-Rilevamento Europa s.r.l. ;Saroli, M.; Università di Cassino e del Lazio Meridionale ;Stramondo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Valensise, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Vannoli, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; ; ; ;; ;; ; ; ; ; ; ; ; On May 20th and 29th, 2012, two earthquakes having magnitude 5.9 and 5.8, respectively, and their aftershocks sequence hit the central Po Plain (Italy), about 40 km north of Bologna, in the northern Apennines. Following the main-shocks, more than 2,000 events were recorded by the INGV National Seismic Network (http://iside.rm.ingv.it/). During the seismic sequence, a pure compressional faulting was generated by the activation of blind thrusts of the western Ferrara Arc, thereby activating a 50 km-long stretch of this buried outer front of the northern Apennines. The focal mechanisms of the larger shocks agree with the compilation of present-day tectonic stress indicators, showing a ca. N-S oriented maximum horizontal stress in the area, i.e. oriented perpendicular to the main structural trends. Most of the seismic sequence was confined between 1 and 12 km depth, above the local basal detachment of the outer thrust front of the northern Apennines. The surface displacement pattern, associated with the mainshocks and some following minor events (some of which above M 5.0), has been measured by applying Interferometric Synthetic Aperture Radar (InSAR) technique to a pair of C-Band Radarsat-1 data. The coseismic movements detected overall the epicentral region have been here used as input information for the source inversion model.486 42 - PublicationOpen AccessCalibration of atmospheric effects on SAR interferograms by GPS and local atmosphere models: first results(2001)
; ; ; ; ; ;Bonforte, A.; Istituto Internazionale di Vulcanologia - CNR, Catania ;Ferretti, A.; Politecnico di Milano ;Prati, C.; Politecnico di Milano ;Puglisi, G.; Istituto Internazionale di Vulcanologia - CNR, Catania ;Rocca, F.; Politecnico di Milano; ;; ; A comparison between the ZPD (Zenith Path Delay), obtained from GPS measurements, and the expected delay, derived from models used to compensate tropospheric effects on SAR interferograms, is made. The results of the two methods are comparable, though the available data set is not large enough for a complete statistical validation of the methods. The results of this preliminary study suggest a possible integration of GPS-based ZPD data with cheap and standard meteorological data, since the estimated atmospheric component proved to be similar. Furthermore, the impact on volcanology of the effects measured by GPS, and in particular on the determination of the depth of the volcanic sources, is discussed.233 535 - PublicationOpen AccessThe Sentinel-1 mission for the improvement of the scientific understanding and the operational monitoring of the seismic cycle(2012)
; ; ; ; ; ; ;Salvi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Stramondo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Funning, G. J.; University of California ;Ferretti, A.; TeleRilevamento Europa ;Sarti, F.; European Space Agency – ESA/ESRIN ;Mouratidis, A.; European Space Agency – ESA/ESRIN; ; ; ;; We describe the state of the art of scientific research on the earthquake cycle based on the analysis of Synthetic Aperture Radar (SAR) data acquired from satellite platforms. We examine the achievements and the main limitations of present SAR systems for the measurement and analysis of crustal deformation, and envision the foreseeable advances that the Sentinel-1 data will generate in the fields of geophysics and tectonics. We also review the technological and scientific issues which have limited so far the operational use of satellite data in seismic hazard assessment and crisis management, and show the improvements expected from Sentinel-1 data226 500 - PublicationRestrictedDynamics of Mt. Etna before, during and after the July - August 2001 eruption inferred from GPS and DInSAR data(2008-06-20)
; ; ; ; ; ; ;Puglisi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Bonforte, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Ferretti, A.; Tele-Rilevamento Europa, Milan, Italy ;Guglielmino, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Palano, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Prati, C.; Dipartimento di Elettronica e Informazione, Politecnico di Milano, Milan, Italy; ; ;; ; Ground deformation data from GPS and differential synthetic aperture radar interferometry (DInSAR) techniques are analyzed to study the July–August 2001 Mount Etna eruption as well as the dynamics preceding and following this event. Five GPS surveys were carried out on the entire Mount Etna network or on its southeastern part, from July 2000 to October 2001. Five ERS-2 ascending passes and three descending ones are used to form five interferograms spanning periods from a month to 1 year, before and encompassing the eruption. Numerical and analytical inversions of the GPS and DInSAR data were performed to obtain analytical models for preeruptive, syneruptive and posteruptive periods. The deformation sources obtained were from the Mogi model: (1) pressure sources located beneath the upper western flank of the volcano, inflating before the eruption onset and deflating afterward; (2) tensile dislocations to model the intrusion of a N-S dike in the central part of the volcano; and (3) two sliding and two normal dislocations to model the eastern and southern flank dynamics. This study confirms that the lower vents of the eruption were fed by a magma stored at depth ranging from 9 to 4 km below sea level, as proposed from petrochemical and geophysical researches. The rising of the magma through the shallow crust started months before the eruption onset but accelerated on the last day; this study suggests that in the volcanic pile the path of the rising magma was driven by the volcano topography. The eastern sliding plane and the interaction between dike intrusion and flank instability have been better defined with respect to previous studies. The sliding motion abruptly accelerated with the dike intrusion, and this continued after the end of the eruption. The acceleration was accompanied by the propagation of the strain field toward the eastern periphery of the volcano.238 37 - PublicationOpen AccessThe VELISAR initiative for the measurement of ground velocity in italian seismogenic areas(2007-04-15)
; ; ; ; ; ; ; ; ; ; ; ; ;Salvi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Atzori, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Brunori, C. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Doumaz, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Ricciardi, G. P.; CNR - IREA, Napoli, Italy ;Solaro, G.; CNR - IREA, Napoli, Italy ;Stramondo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Tolomei, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Lanari, R.; CNR - IREA , Napoli, Italy ;Pepe, A.; CNR - IREA, Napoli, Italy ;Ferretti, A.; Tele Rilevamento Europa S.R.L. Milano, Italy ;Cespa, S.; Tele Rilevamento Europa S.R.L. Milano, Italy; ; ; ; ; ; ; ; ; ; ;VELISAR (Ground VELocity in Italian Seismogenic Areas) is a scientific research initiative aimed at producing a map of the ground deformation over most of the seismogenic areas of Italy, using the space-based technique of multitemporal Synthetic Aperture Radar Interferometry (InSAR). The ground velocities derived from InSAR data will be validated by means of ground based data obtained from GPS, optical leveling, seismological and neotectonic studies. The scope of the project is to produce a high-resolution ground deformation dataset useful to model the seismic cycle of strain accumulation and release at the scale of the single faults. The main objective of VELISAR is to produce maps of ground velocity with the following characteristics: - A ground resolution better than 100 m. - Average uncertainty of LoS velocity measurements smaller than 2 mm/yr . - Temporal coverage of at least 7 years. - Retrieval of East and Up components from ascending and descending LoS. VELISAR will exploit the potential of the long time series (1992-2000) of ERS InSAR data maintained in the ESA archives; over 4000 ERS images will have to be processed to accomplish its objectives. Presently, two InSAR techniques for the measurement of slow ground deformation are used in VELISAR: the Permanent Scatterers (PS) technique developed by the Politecnico of Milano (POLIMI), and the Small Baseline Subset (SBAS) technique, developed by the Institute for Remote Sensing of Environment (IREA-CNR), in Napoli. The PS technique is applied by TRE preferably over areas characterised by diffuse temporal decorrelation due to, for instance, erodible lithologies, agricultural land use and strong vegetation cover. In these areas we expect to obtain good temporal coherence mainly on sparse point scatterers. The SBAS technique is applied by IREA and INGV mostly over areas where limited temporal decorrelation is expected: urban areas, scarcely vegetated areas. The ground resolution at which these data are originally processed is 80 m. An important goal of the VELISAR initiative is to disseminate the information on the InSAR-derived ground velocity measurements, to the scientific community and to the public in general. Such goal is accomplished through a dedicated web site, where the velocity maps of the italian seismogenic areas will be progressively published. We will present the initiative, its scope and objectives, the technical details and the data processing strategies, and some examples of ground velocity maps.247 2094 - PublicationRestrictedSubmillimeter Accuracy of InSAR Time Series: Experimental Validation(2007)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ;This paper presents the results of a blind experiment that is performed using two pairs of dihedral reflectors. The aim of the experiment was to demonstrate that interferometric synthetic aperture radar (InSAR) measurements can indeed allow a displacement time series estimation with submillimeter accuracy (both in horizontal and vertical directions), provided that the data are properly processed and the impact of in situ as well as atmospheric effects is minimized. One pair of dihedral reflectors was moved a few millimeters between SAR acquisitions, in the vertical and east–west (EW) directions, and the ground truth was compared with the InSAR data. The experiment was designed to allow a multiplatform and multigeometry analysis, i.e., each re- flector was carefully pointed in order to be visible in both Envisat and Radarsat acquisitions. Moreover, two pairs of reflectors were used to allow the combination of data gathered along ascending and descending orbits. The standard deviation of the error is 0.75 mm in the vertical direction and 0.58 mm in the horizontal (EW) direction. GPS data were also collected during this experiment in order to cross-check the SAR results.92 4