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  • 04.03. Geodesy  (16)
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  • 1
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    Insights into the fragmentation of the Adria Plate (2018)
    Details
    Publication Date: 2020-11-30
    Description: This study gives an interpretation of the current tectonics and kinematics of the Adria Plate, a region mostly coinciding with Italy and its surroundings. We have examined the spatial distribution and kinematics of seismicity by using an updated dataset obtained integrating the available catalogues of earthquakes and focal mechanisms. Moreover, to highlight the distribution of seismicity and of the asso- ciated strain patterns, we have elaborated a seismic flux map of the Italian region, which is a map of the energy released per unit time and per unit area. Seismic flux represents the energy released and provides a synthetic and continuous view of areas with greater seismicity and associated strain patterns with respect to the plot of earthquakes only. The seismic data, and the results of some elaborations car- ried out using these datasets have been compared with the present-day state of stress and slip rates of the major active faults of some sectors of Italy, as well as with the horizontal kinematics highlighted by GPS observations. The distribution and kinematics of earthquakes and active faults, the seismic flux, and GPS velocities, suggest that the Adria Plate is currently behaving as an ensemble of independent blocks rather than as a unique rigid plate. The Adria Plate can be thus subdivided into three major blocks and a number of smaller blocks moving independently under the action of a first-order mechanism related to the ongoing, roughly N-S, Europe-Africa convergence vector. This complicated setting may promote the occurrence of mutual relationships between blocks, and generate peculiar local kinematics causing seis- mic activity. We infer that the great majority of the seismic events occur at the boundaries of the main or minor blocks, and therefore the alignments of seismicity allows the individuation of the different blocks and the main seismogenic belts. A major crustal structure subdivides the Adria Plate into a western and two eastern blocks, and approximately coincides with the axial zone of the Apennines along which most of the seismicity is concentrated.
    Description: Published
    Description: 121-138
    Description: 1T. Deformazione crostale attiva
    Description: 1IT. Reti di monitoraggio
    Description: 4IT. Banche dati
    Description: JCR Journal
    Keywords: Adria plate ; Apennines ; Active tectonics ; Seismicity ; Seismic flux ; GPS ; 04.06. Seismology ; 04.03. Geodesy ; 04.07. Tectonophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Present-day uplift of the European Alps: Evaluating mechanisms and models of their relative contributions (2020)
    Elsevier
    Details
    Publication Date: 2021-06-25
    Description: Recent measurements of surface vertical displacements of the European Alps show a correlation between vertical velocities and topographic features, with widespread uplift at rates of up to ~2–2.5 mm/a in the North-Western and Central Alps, and ~1 mm/a across a continuous region from the Eastern to the South-Western Alps. Such a rock uplift rate pattern is at odds with the horizontal velocity eld, characterized by shortening and crustal thickening in the Eastern Alps and very limited deformation in the Central and Western Alps. Proposed me- chanisms of rock uplift rate include isostatic response to the last deglaciation, long-term erosion, detachment of the Western Alpine slab, as well as lithospheric and surface de ection due to mantle convection. Here, we assess previous work and present new estimates of the contributions from these mechanisms. Given the large range of model estimates, the isostatic adjustment to deglaciation and erosion are su cient to explain the full observed rate of uplift in the Eastern Alps, which, if correct, would preclude a contribution from horizontal shortening and crustal thickening. Alternatively, uplift is a partitioned response to a range of mechanisms. In the Central and Western Alps, the lithospheric adjustment to deglaciation and erosion likely accounts for roughly half of the rock uplift rate, which points to a noticeable contribution by mantle-related processes such as detachment of the European slab and/or asthenospheric upwelling. While it is di cult to independently constrain the patterns and magnitude of mantle contributions to ongoing Alpine vertical displacements at present, future data should provide additional insights. Regardless, interacting tectonic and surface mass redistribution processes, rather than an individual forcing, best explain ongoing Alpine elevation changes.
    Description: Published
    Description: 589-604
    Description: 1T. Struttura della Terra
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
    Keywords: 04. Solid Earth ; 04.03. Geodesy ; 04.07. Tectonophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    New insights into active tectonics and seismogenic potential of the Italian Southern Alps from vertical geodetic velocities (2020)
    Copernicus
    Details
    Publication Date: 2020-09-07
    Description: This study presents and discusses horizontal and vertical geodetic velocities for a low strain rate region of the south Alpine thrust front in northeastern Italy obtained by integrating GPS, interferometric synthetic aperture radar (InSAR) and leveling data. The area is characterized by the presence of subparallel, south-verging thrusts whose seismogenic potential is still poorly known. Horizontal GPS velocities show that this sector of the eastern Southern Alps is undergoing ∼1 mm a−1 of NW–SE shortening associated with the Adria–Eurasia plate convergence, but the horizontal GPS velocity gradient across the mountain front provides limited constraints on the geometry and slip rate of the several subparallel thrusts. In terms of vertical velocities, the three geodetic methods provide consistent results showing a positive velocity gradient, of ∼ 1.5 mm a−1, across the mountain front, which can hardly be explained solely by isostatic processes. We developed an interseismic dislocation model whose geometry is constrained by available subsurface geological reconstructions and instrumental seismicity. While a fraction of the measured uplift can be attributed to glacial and erosional isostatic processes, our results suggest that interseismic strain accumulation at the Montello and the Bassano–Valdobbiadene thrusts it significantly contributing to the measured uplift. The seismogenic potential of the Montello thrust turns out to be smaller than that of the Bassano–Valdobbiadene fault, whose estimated parameters (locking depth equals 9.1 km and slip rate equals 2.1 mm a−1) indicate a structure capable of potentially generating a Mw〉6.5 earthquake. These results demonstrate the importance of precise vertical ground velocity data for modeling interseismic strain accumulation in slowly deforming regions where seismological and geomorphological evidence of active tectonics is often scarce or not conclusive.
    Description: Published
    Description: 1681–1698
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
    Keywords: Southern Alps ; Vertical Velocities ; GPS and InSAR integration ; Interseismic Deformation ; Dislocation Model ; Seismic Potential ; 04.03. Geodesy ; 04.07. Tectonophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    Geopositioning time series from offshore platforms in the Adriatic Sea (2021)
    Nature P.G.
    Details
    Publication Date: 2021-01-07
    Description: We provide a dataset of 3D coordinate time series of 37 continuous GNSS stations installed for stability monitoring purposes on onshore and offshore industrial settlements along a NW-SE-oriented and ~100-km-wide belt encompassing the eastern Italian coast and the Adriatic Sea. The dataset results from the analysis performed by using different geodetic software (Bernese, GAMIT/GLOBK and GIPSY) and consists of six raw position time series solutions, referred to IGb08 and IGS14 reference frames. Time series analyses and comparisons evidence that the different solutions are consistent between them, despite the use of different software, models, strategy processing and frame realizations. We observe that the offshore stations are subject to significant seasonal oscillations probably due to seasonal environmental loads, seasonal temperature-induced platform deformation and hydrostatic pressure variations. Many stations are characterized by non-linear time series, suggesting a complex interplay between regional (long-term tectonic stress) and local sources of deformation (e.g. reservoirs depletion, sediment compaction). Computed raw time series, logs files, phasor diagrams and time series comparison plots are distributed via PANGAEA ( https://www.pangaea.de ).
    Description: This research was financed by the Italian Economic Development Ministry in the”CLYPEA-Innovation Network for Future Energy” framework, “subsoil deformations” project.
    Description: Published
    Description: 373
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
    Keywords: GNSS ; offshore platforms ; subsidence ; data processing ; oil/gas exploiting ; 04. Solid Earth ; 04.03. Geodesy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
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    Space–time evolution of crustal deformation related to the Mw 6.3, 2009 L'Aquila earthquake (central Italy) from principal component analysis inversion of GPS position time-series (2020)
    Details
    Publication Date: 2020-03-03
    Description: This article has been accepted for publication in Geophysical Journal International ©: 2014, Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
    Description: In this work, we present a study of the coseismic and post-seismic crustal deformation associ- ated to the Mw 6.3, 2009 April 6 L’Aquila earthquake from the analysis of GPS displacement time-series. We use a principal component decomposition-based inversion method to study the space- and time-dependent evolution of slip on faults without any a priori assumption on the model used to characterize the temporal evolution of crustal deformation. The method adopted allows us to account for the initial post-seismic deformation in estimating the coseismic dis- placements, in a consistent manner for the whole GPS network. We use elastic dislocation theory and a least-squares procedure to invert for the slip distribution on the mainshock fault (Paganica fault) and a second fault (Campotosto fault), where a Mw 5.2 aftershock occurred on April 9. The geometries for these faults are obtained from a singular value decomposition of precisely relocated aftershocks. We find that the use of complex fault geometries is not justified by the GPS observations available. An inversion that accounts for post-seismic slip to occur on both the Paganica and Campotosto faults provides a better fit to the GPS time-series observations, than using only the Paganica fault segment, at a 95 per cent confidence level. Within our resolution, afterslip regions do not migrate over time and are localized on fault patches that are approximately complementary to those of coseismic slip. We find that the position of some relevant afterslip patches is different if the inversion is performed assuming a fixed rake or not. We estimate the parameter a – b of rate- and state-dependent friction on those fault regions accommodating afterslip that are robustly characterized in our inversions. We find values of the order of 10−3, which is near the transition from potentially unstable to nominally stable friction. These results are in agreement with laboratory measurements performed on typical rocks of the L’Aquila region.
    Description: Published
    Description: 174–191
    Description: 1T. Struttura della Terra
    Description: 2T. Deformazione crostale attiva
    Description: 3T. Sorgente sismica
    Description: JCR Journal
    Keywords: 04. Solid Earth ; 04.03. Geodesy ; 04.07. Tectonophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 6
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    Blind source separation problem in GPS time series (2020)
    Springer
    Details
    Publication Date: 2020-03-03
    Description: A critical point in the analysis of ground dis- placement time series, as those recorded by space geodetic techniques, is the development of data-driven methods that allow the different sources of deformation to be discerned and characterized in the space and time domains. Multivariate statistic includes several approaches that can be considered as a part of data-driven methods. A widely used technique is the principal component analysis (PCA), which allows us to reduce the dimensionality of the data space while maintain- ing most of the variance of the dataset explained. However, PCA does not perform well in finding the solution to the so-called blind source separation (BSS) problem, i.e., in recovering and separating the original sources that gener- ate the observed data. This is mainly due to the fact that PCA minimizes the misfit calculated using an L 2 norm (χ 2 ), look- ing for a new Euclidean space where the projected data are uncorrelated. The independent component analysis (ICA) is a popular technique adopted to approach the BSS problem. However, the independence condition is not easy to impose, and it is often necessary to introduce some approximations. To work around this problem, we test the use of a modi- fied variational Bayesian ICA (vbICA) method to recover the multiple sources of ground deformation even in the presence of missing data. The vbICA method models the probability density function (pdf) of each source signal using a mix of Gaussian distributions, allowing for more flexibility in the description of the pdf of the sources with respect to standard ICA, and giving a more reliable estimate of them. Here we present its application to synthetic global positioning system (GPS) position time series, generated by simulating deforma- tion near an active fault, including inter-seismic, co-seismic, and post-seismic signals, plus seasonal signals and noise, and an additional time-dependent volcanic source. We evaluate the ability of the PCA and ICA decomposition techniques in explaining the data and in recovering the original (known) sources. Using the same number of components, we find that the vbICA method fits the data almost as well as a PCA method, since the χ 2 increase is less than 10 % the value cal- culated using a PCA decomposition. Unlike PCA, the vbICA algorithm is found to correctly separate the sources if the correlation of the dataset is low (〈0.67) and the geodetic network is sufficiently dense (ten continuous GPS stations within a box of side equal to two times the locking depth of a fault where an earthquake of Mw 〉 6 occurred). We also provide a cookbook for the use of the vbICA algorithm in analyses of position time series for tectonic and non-tectonic applications.
    Description: Published
    Description: 323–341
    Description: 1T. Struttura della Terra
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
    Keywords: 04. Solid Earth ; 04.03. Geodesy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 7
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    Isostasy, dynamic topography, and the elevation of the Apennines of Italy (2020)
    Elsevier
    Details
    Publication Date: 2020-03-03
    Description: The elevation of an orogenic belt is commonly related to crustal/lithosphere thickening. Here, we discuss the Apennines as an example to show that topography at a plate margin may be controlled not only by isostatic adjustment but also by dynamic, mantle-driven processes. Using recent structural constraints for the crust and mantle we find that the expected crustal isostatic component explains only a fraction of the topography of the belt, indicating positive residual topography in the central Apennines and negative residual topography in the northern Apennines and Calabria. The trend of the residual topography matches the mantle flow induced dynamic topography estimated from regional tomography models. We infer that a large fraction of the Apennines topography is related to mantle dynamics, producing relative upwellings in the central Apennines and downwellings in the northern Apennines and Calabria where subduction is still ongoing. Comparison between geodetic and geological data on vertical motions indicates that this dynamic process started in the early Pleistocene and the resulting uplift appears related to the formation and enlargement of a slab window below the central Apennines. The case of the Apennines shows that at convergent margins the elevation of a mountain belt may be significantly different from that predicted solely by crustal isostasy and that a large fraction of the elevation and its rate of change are dynamically controlled by mantle convection.
    Description: Published
    Description: 163-174
    Description: 1T. Struttura della Terra
    Description: 2T. Deformazione crostale attiva
    Description: JCR Journal
    Keywords: 04. Solid Earth ; 04.03. Geodesy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Creep and locking of a low-angle normal fault: Insights from the Altotiberina fault in the Northern Apennines (Italy) (2018)
    Details
    Publication Date: 2019-04-02
    Description: While low-angle normal faults have been recognized worldwide from geological studies, whether these structures are active or capable of generating big earthquakes is still debated. We provide new constraints on the role and modes of the Altotiberina fault (ATF) in accommodating extension in the Northern Apennines. We model GPS velocities to study block kinematics, faults slip rates and interseismic coupling of the ATF, which is active and accounts, with its antithetic fault, for a large part of the observed chain normal 3 mm/yr tectonic extension. A wide portion of the ATF creeps at the long-term slip rate (1.7 ± 0.3 mm/yr), but the shallow locked portions are compatible with M 〉 6.5 earthquakes. We suggest that positive stress accumulation due to ATF creep is most likely released by more favorable oriented splay faults, whose rupture may propagate downdip along low-angle normal fault surface and reduce the probability of occurrence of a seismic rupture of the shallower locked portion.
    Description: Published
    Description: 4321–4329
    Description: 1T. Deformazione crostale attiva
    Description: 1IT. Reti di monitoraggio
    Description: 5IT. Osservatori
    Description: JCR Journal
    Keywords: 04.03. Geodesy ; 04.07. Tectonophysics
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    Time–Space Evolution of Seismic Strain Release in the Area Shocked by the August 24–October 30 Central Italy Seismic Sequence (2018)
    Details
    Publication Date: 2018-03-16
    Description: In this study, we analyze the space–time evolution of the seismic strain release in the area shocked by the still ongoing Italian Central Apennines seismic crisis started on August 24, 2016 and culminated with the October 30 main shock of Mw 6.5. Specifically, we examine the variation in time and space of the seismic strain release rate with the aim of identifying the presence of peculiar seismicity patterns, such as seismic gaps, according to the seismic cycle theory. To this end, seismic strain rates are checked for consistency with strain rates from GPS measurements to possibly adjust them for missing events due to limited seismic catalog extension or incompleteness at large magnitudes. Our results has revealed that the seismic crisis followed a long-term quiescence of about 310 years, characterized by the absence of M6.5? earthquakes, and marked by an almost steady release of seismic deformation. Such temporal gap started after the occur- rence of two nearby strong events in 1703 (Valnerina and L’Aquila earthquakes with magnitudes of 6.9 and 6.7, respectively) and terminated with the beginning of the current Central Apennines seismic crisis.
    Description: Published
    Description: 1875–1887
    Description: 1T. Deformazione crostale attiva
    Description: 1IT. Reti di monitoraggio
    Description: JCR Journal
    Keywords: Central Apennines ; seismic sequence ; quiescence ; seismic gap ; seismic strain rate ; geodetic strain rate ; 04. Solid Earth ; 04.03. Geodesy ; 04.07. Tectonophysics ; 04.06. Seismology
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 10
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    PyGLog: a Python software for handling GNSS metadata and log-files (2020)
    Details
    Publication Date: 2020-02-27
    Description: Abstract We describe a software developed to handle metadata of Global Navigation Satellite System (GNSS) stations. The number of available GNSS sites in the Euro-Mediterranean and African area has grown significantly in the last decade, pushing toward the development of automatic procedures for the analysis of the raw observations. Currently 〉3000 stations are routinely processed at the GPS data analysis center based on the GAMIT/GLOBK software operating at INGV-Bologna. Here we describe a software, written in Python, developed with the goal of processing metadata associated with continuously operating GNSS stations. The metadata is, generally, an ASCII file associated with each station, containing information about the geodetic antenna, the receiver, the radome model and the antenna offset (distance between the phase center of the antenna and the reference point, depending on the mechanical structure of the antenna mount). Commonly, but not always, GNSS stations metadata are provided in the form of log-files, which are however most of time compiled by human operators and later made available on the web for public access. On the research side these metadata are fundamental for a proper data processing and an accurate estimate of geophysical information, and need to be converted in a particular standard format (station info file), depending on the software adopted for data reduction, with coherent information to not stall the elaboration. The check of metadata coming from a huge amount of GNSS stations from different networks is a time consuming task, which compromises the efficiency of the research job. The software presented in this work aims at automatically update the repository of thousands of station metadata files, checking the coherence of the information and creating the station info files, in different formats, needed for processing, thus requiring a minimum effort for data processing to the operators.
    Description: INGV
    Description: Published
    Description: 1-26
    Description: 2T. Deformazione crostale attiva
    Description: N/A or not JCR
    Keywords: Global Navigation Satellite System, Global Positioning System (GPS) – Continuous GPS (CGPS) – station info – log file – metadata – offset – repository – data processing – station-info. ; 04.03. Geodesy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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