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  • 1
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    Investigating the architecture of the Paganica Fault (2009Mw6.1 earthquake, central Italy) by integrating high-resolution multiscale refraction tomography and detailed geological mapping (2018)
    Details
    Publication Date: 2020-10-13
    Description: This article has been accepted for publication in Geophysical Journal Internationa ©: 2017 Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
    Description: We present a 2-D subsurface image of the Paganica Fault from a high-resolution refraction tomography and detailed geological investigation carried out across part of the northwestern segment of the 20-km-long Paganica–San Demetrio fault-system, and which was responsible of the 2009 April 6 Mw 6.1 L’Aquila earthquake (central Italy). We acquired two seismic profiles crossing the Paganica basin with a dense-wide aperture configuration. More than 30 000 P wave first-arrival traveltimes were input to a non-linear tomographic inversion. The obtained 250–300 m deep 2-D Vp images illuminate the shallow portion of the Paganica Fault, and depict additional unreported splays defining a complex half-graben structure. We interpret local thickening of low-Vp (〈2400 m s−1) and intermediate-Vp (2600–3400 m s−1) regions as syn-tectonic clasticwedges above a high-Vp (3800–5000ms−1) carbonate basement. These results are condensed in a 4.2-km-long section across the Paganica basin, clearly indicating that the Paganica Fault is a mature normal fault cutting the whole upper ∼10 km of the crust. We evaluate a minimum cumulative net displacement of 650 ± 90 m and a total heave of 530 ± 65 m accomplished by the Paganica Fault, respectively. In the conservative hypothesis that the extension started during the Gelasian (1.80–2.59 Ma),we obtain a minimum long-term slip-rate of 0.30 ± 0.07 mm yr−1 and an extension-rate of 0.25 ± 0.06 mm yr−1, respectively. Considering the regional averaged extensional field of ∼1 mm yr−1 obtained from geodetic and geological analyses at 104 yr timescale, we infer that the Paganica Fault accounts for ∼20 per cent of the NE-extension affecting this zone of the central Apennines axis due to the concurrent activity of other parallel normal fault-systems nearby (e.g. the Liri, Velino-Magnola, L’Aquila-Celano and Gran Sasso fault-systems).
    Description: Published
    Description: 403-423
    Description: 1T. Deformazione crostale attiva
    Description: JCR Journal
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Earth modeling and estimation of the local seismic ground motion due to site geology in complex volcanoclastic areas (2006)
    INGV
    Details
    Publication Date: 2019-11-04
    Description: Volcanic areas often show complex behaviour as far as seismic waves propagation and seismic motion at surface are concerned. In fact, the finite lateral extent of surface layers such as lava flows, blocks, differential welding and/or zeolitization within pyroclastic deposits, introduces in the propagation of seismic waves effects such as the generation of surface waves at the edge, resonance in lateral direction, diffractions and scattering of energy, which tend to modify the amplitude as well as the duration of the ground motion. The irregular topographic surface, typical of volcanic areas, also strongly influences the seismic site response. Despite this heterogeneity, it is unfortunately a common geophysical and engineering practice to evaluate even in volcanic environments the subsurface velocity field with monodimensional investigation method (i.e. geognostic soundings, refraction survey, down-hole, etc.) prior to the seismic site response computation which in a such cases is obviously also made with 1D algorithms. This approach often leads to highly inaccurate results. In this paper we use a different approach, i.e. a fully 2D P-wave Çturning rayÈ tomographic survey followed by 2D seismic site response modeling. We report here the results of this approach in three sites located at short distance from Mt. Vesuvius and Campi Flegrei and characterized by overburdens constituted by volcanoclastic deposits with large lateral and vertical variations of their elastic properties. Comparison between 1D and 2D Dynamic Amplification Factor shows in all reported cases entirely different results, both in terms of peak period and spectral contents, as expected from the clear bidimensionality of the geological section. Therefore, these studies suggest evaluating carefully the subsoil geological structures in areas characterized by possible large lateral and vertical variations of the elastic properties in order to reach correct seismic site response curves to be used for engineering projects.
    Description: Published
    Description: JCR Journal
    Description: open
    Keywords: dynamic amplification factor ; seismic ; tomography ; pyroclastic rocks ; finite element method ; 04. Solid Earth::04.04. Geology::04.04.10. Stratigraphy ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion ; 04. Solid Earth::04.06. Seismology::04.06.07. Tomography and anisotropy
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 558711 bytes
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  • 3
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    Seismic reflection data processing in active volcanic areas: an application to Campi Flegrei and Somma Vesuvius offshore (Southern Italy) (2006)
    INGV
    Details
    Publication Date: 2019-11-04
    Description: The Campanian volcanism develops near the sea. Therefore, the geophysical study of the marine environment is a key to a better understanding of the tectonic evolution and the origin of volcanism in the area. An abundance of high quality seismic data in the marine sector, where little direct information is available, is critical to the study of Campanian volcanism. This paper concerns the reprocessing of a seismic reflection dataset acquired in Naples Bay and processed during 1973. Even though the overall data quality was high for that time, of course their acquisition technological limits have been overcome by the new processing. Our reprocessing aimed at: 1) reduction of random noise in the data; 2) removal of unwanted coherent events; 3) reduction of spatial aliasing by means of trace interpolation on Commod Shot Point (CSP) gathering; 4) improvement of resolution of the seismic wavelet with spiking deconvolution algorithms and finally 5) reposition of reflectors in their correct locations in the space-TWT domain by means of dip moveout and post-stack time migration. A comparison between the new and old data shows that the new sections are characterized by a much higher S/N ratio. Diffraction hyperbole has been collapsed. Reverberations, ghosts and multiples have been removed or greatly attenuated, especially between the reflectors of interest, allowing us to follow them with more detail and with greater continuity. Furthermore, data resolution has been boosted by the reprocessing, allowing the interpreter to evaluate reflector position and continuity in greater detail. The reinterpretation phase of such lines, that is already in an advanced stage, will therefore allow us to gain new insights into the structural setting of the bay, with the aim of exploring the connection between tectonics and volcanism.
    Description: Published
    Description: JCR Journal
    Description: open
    Keywords: marine geophysics ; seismic reflection ; 04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology ; 04. Solid Earth::04.06. Seismology::04.06.09. Waves and wave analysis ; 05. General::05.02. Data dissemination::05.02.02. Seismological data
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 1291330 bytes
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  • 4
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    Evidence for active folding and faulting at the northern Apennines mountain front near Bologna, Italy from high resolution seismic reflection profiling (2012)
    American Geophysical Union
    Details
    Publication Date: 2020-02-24
    Description: We have acquired and processed an ∼2 km long high-resolution seismic reflection profile across a segment of the Northern Apennine mountain front (Italy), west of the city of Bologna. The profile, constrained by several wells, targets a long-postulated shallow blind or emergent thrust called the Pede-Apenninic Thrust Fault. Despite decades of reflection seismology in this part of the Apennines, a shallow or emergent structure consistent with the surface geology has yet to be definitively identified, a problem likely caused by the topography of the Apennine front and the traditional focus on deep hydrocarbon targets where the first 0.5 km of strata is poorly imaged. Our seismic data show an ∼300 m deep high-resolution picture of the Po foreland as it meets the Apennine mountain front. All imaged reflectors are continuous at the mountain front and are foreland-dipping, showing clear growth relationships; higher-angle reflectors are interpreted as faults. Our interpretation includes a possible hinterland-dipping blind thrust and surface normal faults, which offset late Pleistocene-Holocene deposits as much as 60 m (long-term slip rates of 0.1–0.25 mm/yr) that disrupt, but do not conceal, the growth strata relationships. Vp tomographic imaging also suggests coseismic surface-faulting in Holocene colluvium. These results have implications relevant for the effective data collection and processing techniques for these kinds of shallow active structures as well as a re-evaluation of the seismogenic potential of densely populated cities like Bologna along the Apennine mountain front.
    Description: Published
    Description: L16302
    Description: JCR Journal
    Description: restricted
    Keywords: Northern Apennines ; 04. Solid Earth::04.06. Seismology::04.06.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 5
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    Investigating the architecture of the Paganica Fault (2009 Mw 6.1 earthquake, central Italy) by integrating high-resolution multiscale refraction tomography and detailed geological mapping (2016)
    Oxford University Press
    Details
    Publication Date: 2016-11-25
    Description: We present a 2-D subsurface image of the Paganica Fault from a high-resolution refraction tomography and detailed geological investigation carried out across part of the northwestern segment of the 20-km-long Paganica–San Demetrio fault-system, and which was responsible of the 2009 April 6 M w 6.1 L'Aquila earthquake (central Italy). We acquired two seismic profiles crossing the Paganica basin with a dense-wide aperture configuration. More than 30 000 P wave first-arrival traveltimes were input to a non-linear tomographic inversion. The obtained 250–300 m deep 2-D Vp images illuminate the shallow portion of the Paganica Fault, and depict additional unreported splays defining a complex half-graben structure. We interpret local thickening of low- Vp (〈2400 m s –1 ) and intermediate- Vp (2600–3400 m s –1 ) regions as syn-tectonic clastic wedges above a high- Vp (3800–5000 m s –1 ) carbonate basement. These results are condensed in a 4.2-km-long section across the Paganica basin, clearly indicating that the Paganica Fault is a mature normal fault cutting the whole upper ~10 km of the crust. We evaluate a minimum cumulative net displacement of 650 ± 90 m and a total heave of 530 ± 65 m accomplished by the Paganica Fault, respectively. In the conservative hypothesis that the extension started during the Gelasian (1.80–2.59 Ma), we obtain a minimum long-term slip-rate of 0.30 ± 0.07 mm yr –1 and an extension-rate of 0.25 ± 0.06 mm yr –1 , respectively. Considering the regional averaged extensional field of ~1 mm yr –1 obtained from geodetic and geological analyses at 10 4  yr timescale, we infer that the Paganica Fault accounts for ~20 per cent of the NE-extension affecting this zone of the central Apennines axis due to the concurrent activity of other parallel normal fault-systems nearby (e.g. the Liri, Velino-Magnola, L'Aquila-Celano and Gran Sasso fault-systems).
    Keywords: Geodynamics and Tectonics
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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