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Rossi, Giuliana
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Rossi, Giuliana
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- PublicationOpen AccessAdaptive regridding in 3D reflection tomography(1997-01)
; ; ; ;Böhm, G.; Osservatorio Geofisico Sperimentale, Trieste, Italy ;Rossi, G.; Osservatorio Geofisico Sperimentale, Trieste, Italy ;Vesnaver, A.; Osservatorio Geofisico Sperimentale, Trieste, Italy; ; 3D reflection tomography allows the macro-model of complex geological structures to be reconstructed. In the usual approach, the spatial distribution of the velocity field is discretized by regular grids. This choice simplifies the development of the related software, but introduces two serious drawbacks: various domains of the model may be poorly covered, and a relevant mismatch between the grid and a complex velocity field may occur. So the tomographic inversion becomes unstable, unreliable and necessarily blurred. In this paper we introduce an algorithm to adapt the grid to the available ray paths and to the velocity field in sequence: so we get irregular grids with a locally variable resolution. We can guide the grid fitting procedure interactively, if we are going to introduce some geological a priori information; otherwise, we define a fully automatic approach, which exploits the Delauny triangles and Voronoi polygons.178 522 - PublicationOpen AccessEditorial: The structure of the central Mediterranean: Insights from seismological and geophysical dataThe mountain chains of the Central Mediterranean (the Apennines, the Alps, the Dinarides, the Albanides, and the Hellenides) are shaped by complex tectonics arising from the motion and collision of several microplates. Intense onshore and offshore seismic activity puts the rich cultural heritage characterising the entire region at risk. A better understanding of the lithospheric structures and knowledge of the interaction between different tectonic units is key to unraveling the processes underlying seismic activity in this area. In recent years, top-quality seismological data from several groundbreaking experiments have yielded new insight into the orogenic systems of the region (e.g., IberArray, AlpArray, and its complementary seismic experiments, or the “THALES WAS RIGHT” EU project). Similar projects are planned to cover other parts of this critical region, for example, AdriaArray, which will cover the Adria microplate and the Balkans with a dense seismological array.
166 13 - PublicationOpen AccessNew evidence of active transtensional deformation in apulia foreland (n-ionian sea).(2018-09-02)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The response of continental forelands to subduction and oblique collision is a widely investigated topic in geodynamics. The deformation occurring within a foreland shared by two opposite-verging chains, however, is not very common and poorly understood. The Apulia block, at the southern end of the Adria microplate, Central Mediterranean, represents one of these latter cases, being the common foreland of the Dinarides and Apennines orogens. In its southern part, the Apulian foreland has preserved the Mesozoic paleomargin at the transition with the old oceanic Ionian crust that conversely underwent subduction under the Calabrian and Hellenic arcs. For these reasons, Apulia represents an interesting and rare case of study where double orogens and subduction have interacted with the foreland block. As described by various authors, the almost symmetrical bending of the Apulia foreland due the opposite load of the adjacent chains, produced a system of NW-SE trending normal faults. The precise age and the role of these faults have not been yet determined due to the lack of available information. In this contribution we investigated the internal deformation of the Apulia foreland using geophysical data at various resolutions and scales over a wide area. We used multichannel seismic profiles, part of which are provided in the collaborative framework between Spectrum Geo and INGV, recorded up to 12 s and provide a consistent imaging of the upper crustal setting of the Apulia foreland. High-resolution multichannel seismic profiles, multibeam high-resolution bathymetry and CHIRP profiles recently acquired by R/V OGS Explora provide constraints on the recent activity of the major fault systems identified. The analysis of this multiscale dataset highlights the presence and the role of a major NW-SE oriented active fault system which obliquely cuts the Apulia foreland. The presence of this fault system has already been hypothesized based on sparse seismic profiles, but its lateral continuity has never been documented. From the seismic viewpoint, this structure lies in a relatively silent area. Nonetheless, it hosts the 1743 Southern Apulia Mw 6.8 earthquake which widely damaged the Salento (S-Italy) and Ionian Islands (Greece) regions and whose source is still a matter of debate. This new geophysical dataset allowed us to reconstruct the 3D geometry of this fault system, whose architecture suggests a transtensive kinematics, and to analyse the syn-tectonic basins associated with the major faults which recorded the Late Quaternary to Holocene deformation. This work is being developed in the frame of the project “FASTMIT”, funded by the Italian Ministry of University and Research.132 34 - PublicationRestrictedA quantitative approach to the loading rate of seismogenic sources in Italy(2018)
; ; ; ; ; ; ; ; ;; ;; ;To investigate the transfer of elastic energy between a regional stress field and a set of localized faults, we project the stress rate tensor inferred from the Italian GNSS (Global Navigation Satellite Systems) velocity field onto faults selected from the Database of Individual Seismogenic Sources (DISS 3.2.0). For given Lamé constants and friction coefficient, we compute the loading rate on each fault in terms of the Coulomb failure function (CFF) rate. By varying the strike, dip and rake angles around the nominal DISS values, we also estimate the geometry of planes that are optimally oriented for maximal CFF rate. Out of 86 Individual Seismogenic Sources (ISSs), all well covered by GNSS data, 78–81 (depending on the assumed friction coefficient) load energy at a rate of 0–4 kPa yr−1. The faults displaying larger CFF rates (4–6 ± 1 kPa yr−1) are located in the central Apennines and are all characterized by a significant strike-slip component. We also find that the loading rate of 75% of the examined sources is less than 1 kPa yr−1 lower than that of optimally oriented faults. We also analysed 2016 August 24 and October 30 central Apennines earthquakes (Mw 6.0–6.5, respectively). The strike of their causative faults based on seismological and tectonic data and the geodetically inferred strike differ by <30°. Some sources exhibit a strike oblique to the direction of maximum strain rate, suggesting that in some instances the present-day stress acts on inherited faults. The choice of the friction coefficient only marginally affects this result.381 1 - PublicationOpen AccessActive Extension in a Foreland Trapped Between Two Contractional Chains: The South Apulia Fault System (SAFS)(2020-06-11)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The response of continental forelands to subduction and collision is a widely investigated topic in geodynamics. The deformation occurring within a foreland shared by two opposite‐verging chains, however, is uncommon and poorly understood. The Apulia Swell in the southern end of the Adria microplate (Africa‐Europe plate boundary, central Mediterranean Sea) represents one of these cases, as it is the common foreland of the SW verging Albanides‐Hellenides and the NE verging Southern Apennines merging into the SSE verging Calabrian Arc. We investigated the internal deformation of the Apulia Swell using multiscale geophysical data: multichannel seismic profiles recording up to 12‐s two‐way time (TWT) for a consistent image of the upper crust; high‐resolution multichannel seismic profiles, high‐resolution multibeam bathymetry, and CHIRP profiles acquired by R/V OGS Explora to constrain the Quaternary geological record. The results of our analyses characterize the geometry of the South Apulia Fault System (SAFS), a 100‐km‐long and 12‐km‐wide structure attesting an extensional (and possibly transtensional) response of the foreland to the two contractional fronts. The SAFS consists of two NW‐SE right‐stepping master faults and several secondary structures. The SAFS activity spans from the Early Pleistocene through the Holocene, as testified by the bathymetric and high‐resolution seismic data, with long‐term slip rates in the range of 0.2–0.4 mm/yr. Considering the position within an area with few or none other active faults in the surroundings, the dimension, and the activity rates, the SAFS can be a candidate causative fault of the 20 February 1743, M 6.7, earthquake.709 37 - PublicationOpen AccessPresent-Day Surface Deformation in North-East Italy Using InSAR and GNSS Data(2023)
; ; ; ; ; ; ; ; ; ; ;; ;; ;Geodetic data can detect and estimate deformation signals and rates due to natural and anthropogenic phenomena. In the present study, we focus on northeastern Italy, an area characterized by ~1.5–3 mm/yr of convergence rates due to the collision of Adria-Eurasia plates and active subsidence along the coasts. To define the rates and trends of tectonic and subsidence signals, we use a Multi-Temporal InSAR (MT-InSAR) approach called the Stanford Method for Persistent Scatterers (StaMPS), which is based on the detection of coherent and temporally stable pixels in a stack of single-master differential interferograms. We use Sentinel-1 SAR images along ascending and descending orbits spanning the 2015–2019 temporal interval as inputs for Persistent Scatterers InSAR (PSI) processing. We apply spatial-temporal filters and post-processing steps to reduce unrealistic results. Finally, we calibrate InSAR measurements using GNSS velocities derived from permanent stations available in the study area. Our results consist of mean ground velocity maps showing the displacement rates along the radar Line-Of-Sight for each satellite track, from which we estimate the east–west and vertical velocity components. Our results provide a detailed and original view of active vertical and horizontal displacement rates over the whole region, allowing the detection of spatial velocity gradients, which are particularly relevant to a better understanding of the seismogenic potential of the area. As regards the subsidence along the coasts, our measurements confirm the correlation between subsidence and the geological setting of the study area, with rates of ~2–4 mm/yr between the Venezia and Marano lagoons, and lower than 1 mm/yr near Grado.79 5