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  • 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous  (13)
  • 04. Solid Earth::04.06. Seismology::04.06.01. Earthquake faults: properties and evolution  (6)
  • Benevento  (2)
  • 1
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    Controlled source non-linear tomography: a powerful tool to constrain tectonic models of the Southern Apennines orogenic wedge, Italy (2007)
    Details
    Publication Date: 2017-04-04
    Description: The anatomy of the Southern Apennines is a matter of compelling debate. Both thick- and thin-skinned tectonic models are proposed due to paucity of deep seismic constraints. We yield new and firmly constrained information on the velocity structure of the mountain range by using an innovative, nonlinear tomographic technique applied to refraction/wide-angle reflection data. Remarkably, the obtained velocity/interface model shows a very high velocity region, with values exceeding 7 km/s, at 8–9 km depth. Such large velocities cannot be related to sedimentary rocks, and imply the presence of shallow crystalline rocks, i.e., the basement involvement in the thrust belt. The integration of our results with other geophysical data (local earthquake tomography, Bouguer and magnetic anomalies) confirms this interpretation that strongly supports thick-skinned tectonics and has significant implications for the seismotectonics and hydrocarbon potential of the Southern Apennines. Our inversion approach can be effective in other orogenic wedges, when seismic reflection profiling fails to uniquely resolve deep complex structures.
    Description: Published
    Description: 941-944
    Description: reserved
    Keywords: Southern Apennines, crustal structure, nonlinear tomography, thick-skinned tectonics. ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 2
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    Quantitative imaging of complex structures from multi-fold wide-aperture seismic data: a case study (2007)
    Details
    Publication Date: 2017-04-04
    Description: An integrated multi-scale seismic imaging flow including first-arrival traveltime tomography and waveform inversion is applied to dense onshore wide-aperture seimsic data recorded in a complex geological setting (southern Apennines thrust belt, Italy)
    Description: Published
    Description: 625-651
    Description: open
    Keywords: comlex media, traveltime inversion, waveform inversion, wide-aperture data ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 3
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    An integrated geophysical investigation of the upper crust in the epicentral area of the 1980, Ms=6.9, Irpinia earthquake (Southern Italy) (2007)
    Details
    Publication Date: 2017-04-04
    Description: In this paper we investigate the upper crustal structure of the Irpinia region, Southern Apennines thrust-belt, Italy, through analysis and joint interpretation of gravity data, seismic reflection lines and subsurface information from many deep wells. The investigated region includes the epicentral area of the 1980 (Ms=6.9) Irpinia earthquake and is one of the Italian regions with the highest seismic hazard. The upper crustal structure is imaged by modeling a series of 15 SW-trending gravity profiles, about 5 km spaced, plentifully constrained by seismic reflection lines and wells, thus reducing the inherent ambiguity of the gravity modeling. Despite of the complexity of the modeled Bouguer anomalies, the application of a calibrating procedure to constrain the range of variability of the density values, as well as the use of geometric constraints, result in a good level of stability in the final density cross-sections, which appear in fact coherent both in the density values and in the geometrical features. The inferred model shows important lateral density variations, which can be mostly related to NW-trending geologic structures. High density bodies delineate carbonate platform thrust-sheets and broad antiforms involving Mesozoic basinal rocks, while low-density shallow bodies are associated with Pliocene basins. In addition, important density (i.e. lithological) variations are evident along the strike of the range, the most relevant being an abrupt deepening of the Apulia Carbonate Platform in the southeastern part of the investigated region. In the epicentral region of the 1980 event, we find that the geometry of the high-density, high-velocity carbonates of the Apulia Platform appears correlated with the distribution of the aftershocks and with the P-wave velocity anomaly pattern as inferred from a previous local earthquake tomography. The structural highs of the Apulia Platform correspond to high-velocity regions, where aftershocks and coseismic slip of the mainshock concentrated. This correlation suggests that the Apulia Carbonate Platform geometry played an important role in the rupture propagation and in the aftershock distribution
    Description: Published
    Description: 139-169
    Description: reserved
    Keywords: Southern Apennines, crustal structure, 1980 Irpinia earthquake, gravity data, seismic profiles, oil exploration wells ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 4
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    Inferences on upper crustal structure of the Southern Apennines (Italy) from seismic refraction investigations and subsurface data (2007)
    Details
    Publication Date: 2017-04-04
    Description: This paper presents an interpretation of crustal seismic refraction data from the northern sector of the Southern Apennines thrust belt, a region that in historical times experienced large destructive earthquakes. The data were acquired in 1992 along a seismic line 75 km long and parallel to the Apenninic chain, in order to determine a detailed 2-D P-wave velocity model of the upper crust in an area that had not been deeply investigated by geophysical methods previously. We have used a 2-D ray tracing technique based on asymptotic ray theory to model travel times of first and reflected P-wave arrivals. Synthetic seismograms have been produced by finite difference simulations in order to check the reliability of the velocity model inferred by ray-tracing modelling. The interpretation of the velocity model is constrained by stratigraphic and sonic velocity logs from wells for oil exploration located close to the seismic line. Gravity data modelling allows to check the velocity model and to extend the structural interpretation in 3-D. In the shallow crust, up to a depth of 3–4 km, strong lateral variations of the modelled velocities are produced by the overlapping of thrust sheets formed by: (1) Cenozoic flyschoid cover and basinal successions that underlie the seismic profile with P-wave velocities in the 2.8–4.1 km/s range and thicknesses varying between 0.5 and 4.5 km; (2) Mesozoic basinal sequences with a velocity of 4.8 km/s and a depth of 1.5–2.1 km in the northern part of the profile; (3) Mesozoic limestones of the Western Carbonate Platform with a velocity of 6.0 km/s and a depth of 0.1–0.8 km in the southern part of the profile. At a greater depth, the model becomes more homogeneous. A continuous seismic interface 3.0–4.5 km deep with a velocity of 6.0 km/s is interpreted as the top of the Meso-Cenozoic Carbonate Multilayer of the Apulia Platform, characterized by an increase in seismic velocity from 6.2 to 6.6 km/s at depths of 6–7 km. A lower P-wave velocity (about 5.0 km/s) is hypothesized at depths ranging between 9.5 and 11 km. As inferred by commercial seismic lines and data from two deep wells located in the Apulia foreland and Bradano foredeep, this low-velocity layer can be related to Permo-Triassic clastic deposits drilled at the bottom of the Apulia Platform. Seismic data do not allow us to identify possible deeper seismic interfaces that could correspond to the top of the Paleozoic crystalline basement; this is probably due to the low-velocity layer at the bottom of the Carbonate Multilayer that reflects and attenuates a great part of the seismic energy. The joint interpretation of seismic refraction and well data, in accordance with gravity data, provides the first detailed P-wave velocity model of the upper crust of the northern sector of the Southern Apennines, which differs considerably from previous 1-D velocity models used to study the seismicity of the region, and reveals new information about the structure of the thrust belt
    Description: Published
    Description: 273-297
    Description: reserved
    Keywords: crustal structure; Italy; seismic refraction; Southern Apennines ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 5
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    A study of the seismic response of the city of Benevento (southern Italy) through a combined analysis of seismological and geological data (2008)
    elsevier
    Details
    Publication Date: 2017-04-04
    Description: A previous analysis (Improta et al., 2005) of small magnitude earthquakes recorded at 12 sites within the city of Benevento has stressed the significant role played by near-surface geology in causing variability of the ground motion. In this paper, we extend the study of the seismic response of the city from 12 sites to the entire urban area. We analyze more than 250 boreholes to constrain the near-surface geology in as many as possible sites. In spite of this geological dataset, uncertainties on the subsoil structure remain due to the presence of strong lithological heterogeneities which are responsible for rapid change of the shallow S-wave velocities (from 200 to 1700 m/s). Therefore, based on inferences from the comparison at the 12 sites between earthquake and ambient vibration results, we have collected ambient noise at about 100 sites within the city, intensifying measurements where geological variations occurs. Microtremor H/V spectral ratios are interpreted in terms of near-surface geology and compared to theoretical transfer functions of 1D models along five well-constrained profiles. On the basis of geological, geotechnical, and seismic data, we identify three main typologies of seismic response. Each type of response is associated to zones of the city sharing common soil conditions and similar soil classes according to building codes for seismic design. Moreover, we find that the spatial variation of the seismic response in the old town area is consistent with the damage pattern produced by a very destructive, well-documented historical earthquake that struck the city in 1688, causing intensity of IX-X MCS in Benevento. Finally, we use ground motions recorded during the experiment by Improta et al. (2005) to generate synthetic seismograms of moderate to strong (Ms 6.9, 1980 Irpinia and Mw 5.7, Molise 2002) earthquakes. We calibrate the random summation technique by Ordaz et al. (1995) using recordings of these earthquakes available in Benevento. After a satisfactory fit between observed and synthetic seismograms, we compute response spectra at different sites and speculate on effects of the geology class at large level of shaking, including soil nonlinearity. We find that large discrepancies with design spectra can occur for a wide sector of Benevento, especially for periods 〈 0.5 sec.
    Description: Published
    Description: 146-170
    Description: 4.1. Metodologie sismologiche per l'ingegneria sismica
    Description: JCR Journal
    Description: partially_open
    Keywords: site effects ; ambient noise ; Empirical Green's Functions ; Response Spectra ; Benevento ; 04. Solid Earth::04.06. Seismology::04.06.04. Ground motion
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 6
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    High-resolution imaging of basin-bounding normal faults in the Southern Apennines seismic belt (Italy) by traveltime and frequency-domain full-waveform tomography (2008)
    Details
    Publication Date: 2017-04-04
    Description: We apply a two-step seismic imaging flow by combined first-arrival traveltime and frequency-domain waveform tomographies to dense wide aperture data collected in the Val d’Agri basin (southern Italy). A large wavelength Vp model determined by first-arrival traveltime tomography is used as a starting model for waveform tomography. The multiscale waveform tomography consisting of successive inversion of increasing frequencies allows to progressively reconstruct the short wavelengths of the velocity model, providing valuable information on the Quaternary basin and on range-bounding normal-faulting systems.
    Description: Published
    Description: Rome
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: open
    Keywords: Seismic Tomography ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: Conference paper
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  • 7
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    Combining seismic reflection with multifold wide-aperture profiling: An effective strategy for high-resolution shallow imaging of active faults (2007)
    AGU
    Details
    Publication Date: 2017-04-04
    Description: Shallow imaging of fault zones is a challenging task. We investigate if this issue can be successfully addressed by combining reflection seismics with non-standard multifold wide-aperture profiling, a strategy pertaining to crustal scale exploration so far. Near-offset reflection and multifold wide-aperture data are simultaneously recorded along two profiles in a small basin crossed by an active fault in Southern Italy. Imaging consists of multiscale seismic tomography complemented by CDP processing of near-offset reflections and of data spanning a large offset range. By combining smooth Vp and reflectivity images we pinpoint the fault location and yield a valuable picture of the basin. Performance of each exploration technique strongly varies in the two surveys depending on the local geologic conditions. Thus, the combined exploration strategy not only yields complementary images for enhanced interpretation, but also allows extending the range of applicability of shallow seismics for fault detection, reducing the risk of unsuccessful investigations.
    Description: Published
    Description: L20310
    Description: 3.3. Geodinamica e struttura dell'interno della Terra
    Description: JCR Journal
    Description: reserved
    Keywords: shallow fault imaging ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 8
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    Ultrashallow seismic imaging of the causative fault of the 1980, M6.9, southern Italy earthquake by pre‐stack depth migration of dense wide‐aperture data (2010)
    AGU
    Details
    Publication Date: 2012-02-03
    Description: An edited version of this paper was published by AGU. Copyright (2010) American Geophysical Union.
    Description: Pre-Stack Depth Migration (PSDM) is an effective tool to improve seismic reflection imaging of laterally heterogeneous media. However, migration performance strongly depends on the accuracy of the velocity model, therefore, PSDM is often ineffective for ultrashallow imaging (100 m and less) of complex structures. In this study, we applied non-linear multiscale refraction tomography and PSDM on dense wide-aperture data to image the causative fault of the 1980, M6.9, Irpinia normal faulting earthquake in a very complex geologic environment. Dense wide-aperture profiling allowed us to build accurate velocity models by multi-scale non linear refraction tomography and to record wide-angle reflections from steep reflectors. PSDM provided superior imaging with respect to conventional post-stack depth migration, and a better definition of fault geometry and apparent cumulative displacement. The estimated throw of Irpinia fault is only 29-38 m. This value, combined with the vertical slip rate estimated by nearby trenches, suggests a young age (97-127 kyr) of fault inception. Our outcomes are in agreement with paleoseismic data and indicate that this imaging strategy can be very effective for near-surface fault detection and characterization.
    Description: Grant L.R. n. 5/2002 - Annuity 2003 - to Pier Paolo Bruno
    Description: Published
    Description: L19302
    Description: 3.2. Tettonica attiva
    Description: JCR Journal
    Description: reserved
    Keywords: pre-stack migration, seismic reflection, seismic tomography, irpinia fault ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 9
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    Multiscale imaging of complex structures from multi-fold wide-aperture seismic data by frequency-domain full-waveform inversion: application to a thrust belt (2007)
    Details
    Publication Date: 2017-04-04
    Description: An application of full-waveform tomography to dense onshore wide-aperture seismic data recorded in a complex geological setting (thrust belt) is presented. The waveform modelling and tomography are implemented in the frequency domain. The modelling part is solved with a finite-difference method applied to the visco-acoustic wave equation. The inversion is based on a local gradient method. Only the P-wave velocity is involved in the inversion. The inversion is applied iteratively to discrete frequency components by proceeding from low to high frequencies. This defines a multiscale imaging in the sense that high wavenumbers are progressively incorporated in images. The linearized waveform tomography requires an accurate starting velocity model that has been developed by first-arrival traveltime tomography. After specific pre-processing of the data, 16 frequency components ranging between 5.4 and 20 Hz were inverted. Ten iterations were computed per frequency component leading to 160 tomographic models. The waveform tomography has successfully imaged southwest dipping structures previously identified from other geophysical data as being associated with high-resistivity bodies. The relevance of the tomographic images is locally demonstrated by comparison of a velocity–depth function extracted from the waveform tomography models with a coincident vertical seismic profiling (VSP) log available on the profile. Moreover, comparison between observed and synthetic seismograms computed in the (starting) traveltime and waveform tomography models demonstrates unambiguously that the waveform tomography successfully predicts for wide-angle reflections from southwest-dipping geological structures. This study demonstrates that the combination of first-arrival traveltime and frequency domain full-waveform tomographies applied to dense wide-aperture seismic data is a promising approach to quantitative imaging of complex geological structures. Indeed, wide-aperture acquisition geometries offer the opportunity to develop an accurate background velocity model for the subsequent waveform tomography. This is critical, because the building of the macromodel remains an open question when only near-vertical reflection data are considered.
    Description: Published
    Description: 1032-1056
    Description: open
    Keywords: finite-difference methods, thrust belt, traveltime and full waveform inversions, ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
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  • 10
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    Seismic imaging of complex structures by non-linear traveltime inversion of dense wide-angle data: application to a thrust belt (2007)
    Details
    Publication Date: 2017-04-04
    Description: A dense wide-angle data set is used to test a two-step procedure for the separate inversion of first-arrival and reflection traveltimes. Data were collected in a complex thrust belt environment (southern Italy) along a 14 km line, with closely spaced sources (60 m) and receivers (90 m). A fully non-linear tomographic technique, that is specially designed to image complex structures, is applied to over 6400 first-arrival traveltimes in order to determine a detailed velocity model. A bi-cubic spline velocity model parameterization is used. The inversion strategy follows a multiscale approach and employs a non-linear velocity optimization scheme. The tomographic velocity model is adopted as the background reference medium for a subsequent interface inversion, which is aimed at imaging a target upper-crust reflector. The interface inversion method is also based on a multiscale approach and uses a non-linear technique for model parameters (interface position nodes) optimization. It is applied to over 1600 reflection traveltimes of a target event picked both in the near- and in the wide-angle offset range. The retrieved interface is well resolved in central part of the model, where ray coverage mainly includes clear post-critical reflections and the background velocity model is accurate in depth thanks to large offset deep turning rays. The determined velocity and interface models are consistent with VSP data and correlate well with the geometry of known geologic structures. This study shows that the used inversion approach is efficient for target-orientated investigations in complex geologic environments
    Description: Published
    Description: 264-278
    Description: reserved
    Keywords: dense wide-angle data, transmission tomography, interface inversion, non-linear inversion, complex geologic environment ; 04. Solid Earth::04.02. Exploration geophysics::04.02.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Format: 3228587 bytes
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