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  • 1
    Electronic Resource
    Electronic Resource
    Quantitative imaging of complex structures from dense wide-aperture seismic data by multiscale traveltime and waveform inversions: a case study (2004)
    PO Box 1354, 9600 Garsington Road , Oxford OX4 2XG , UK . : Blackwell Science Ltd
    Geophysical prospecting 52 (2004), S. 0 
    Details
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: An integrated multiscale seismic imaging flow is applied to dense onshore wide-aperture seismic data recorded in a complex geological setting (thrust belt).An initial P-wave velocity macromodel is first developed by first-arrival traveltime tomography. This model is used as an initial guess for subsequent full-waveform tomography, which leads to greatly improved spatial resolution of the P-wave velocity model. However, the application of full-waveform tomography to the high-frequency part of the source bandwidth is difficult, due to the non-linearity of this kind of method. Moreover, it is computationally expensive at high frequencies since a finite-difference method is used to model the wave propagation. Hence, full-waveform tomography was complemented by asymptotic prestack depth migration to process the full-source bandwidth and develop a sharp image of the short wavelengths. The final traveltime tomography model and two smoothed versions of the final full-waveform tomography model were used as a macromodel for the prestack depth migration.In this study, wide-aperture multifold seismic data are used. After specific preprocessing of the data, 16 frequency components ranging from 5.4 Hz to 20 Hz were inverted in cascade by the full-waveform tomography algorithm. The full-waveform tomography successfully imaged SW-dipping structures previously identified as high-resistivity bodies. The relevance of the full-waveform tomography models is demonstrated locally by comparison with a coincident vertical seismic profiling (VSP) log available on the profile. The prestack depth-migrated images, inferred from the traveltime, and the smoothed full-waveform tomography macromodels are shown to be, on the whole, consistent with the final full-waveform tomography model. A more detailed analysis, based on common-image gather computations, and local comparison with the VSP log revealed that the most accurate migrated sections are those obtained from the full-waveform tomography macromodels. A resolution analysis suggests that the asymptotic prestack depth migration successfully migrated the wide-aperture components of the data, allowing medium wavelengths in addition to the short wavelengths of the structure to be imaged.The processing flow that we applied to dense wide-aperture seismic data is shown to provide a promising approach, complementary to more classical seismic reflection data processing, to quantitative imaging of complex geological structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.2004.00452.x
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    The effect of acetylsalicylic acid on insulin response to glucose and arginine in normal man (1978)
    Springer
    Diabetologia 14 (1978), S. 359-362 
    Details
    ISSN: 1432-0428
    Keywords: Acetylsalicylic acid ; glucose ; insulin ; intravenous glucose tolerance test ; arginine test ; prostaglandins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In 14 normal subjects, treatment with acetylsalicylic acid (ASA, 3.2 g daily for 3 days) a well known inhibitor of prostaglandin synthesis, caused a slight but significant decrease (p〈0.05) in basal plasma glucose levels; by contrast, basal insulin rose from 5±1 to 8±1 μU/ml (p〈0.01) after ASA. Pretreatment with ASA augmented the early insulin response to a standard IV glucose tolerance test (25 g) in 7 normal subjects (p〈0.05 at 2 min; p〈0.02 at 5 min; p〈0.01 at 10 min). No significant changes were detected in the rate of glucose utilization. 7 additional subjects received a standard arginine test without and with ASA pretreatment. Arginine stimulated insulin levels were increased after ASA (p〈0.01 at 15 min; p〈0.05 at 30 min; p〈0.05 at 45 min), whereas glucose values were lower than under basal conditions at all times, with significant differences at 105 (p〈0.02) and 120 (p〈0.05) min. A possible role of prostaglandins upon the insulin responses to glucose and arginine is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01228129
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  • 3
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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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  • 4
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    High-Resolution Densely Spaced Wide-Aperture Seismic Profiling as a Tool to Aid Seismic Hazard Assessment of Fault-Bounded Intramontane Basins: Application to Vallo di Diano, Southern Italy (2013)
    Seismological Society of America (SSA)
    Details
    Publication Date: 2013-06-08
    Description: Seismic hazards in extensional regions are mostly posed by high-angle normal faults and deep hanging-wall basins that can promote significant ground-motion amplifications. Characterized by strong lateral velocity variations, these structures represent challenging targets for seismic exploration. In this paper, we show that prestack depth migration of high-resolution seismic-reflection data, collected with nonconventional dense wide-aperture arrays, can effectively assist deterministic seismic-hazard assessment of fault-bounded basins. Our high-resolution 3.2 km long seismic profile was acquired along Vallo di Diano, the largest fault-bounded intramontane basin in the southern Apennines seismic belt (Italy). The imaging strategy combines prestack depth migration with an iterative velocity-building technique that utilizes results of multiscale refraction tomography. In particular, migration of steeply dipping reflections is essential in imaging the complex morphology of the basement rocks beneath the basin. By combining seismic-reflection and V P tomography results we were able to evaluate (1) the structure of the Vallo di Diano basin along a representative transect from near-surface to basement depths; (2) the shallow-depth geometry of the Vallo di Diano fault system, which bounds the basin to the east; (3) the structure of the sediment–basement interface; and (4) the velocity structure of basement and sediments within the basin. These findings are valuable both for understanding the tectonic evolution of the Vallo di Diano and for developing earthquake-shaking scenario studies.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
    Published by Seismological Society of America (SSA)
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  • 5
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    A detailed analysis of wastewater induced seismicity in the Val d'Agri oil field (Italy) (2015)
    Wiley-Blackwell
    Details
    Publication Date: 2015-03-25
    Description: The Val d'Agri basin in the Apennines seismic belt hosts the largest oil field in onshore Europe. High-quality recordings from a temporary dense network unravel a swarm of 111 small-magnitude events (M L ≤ 1.8) occurred in June 2006 during the first stage of wastewater injection into a high-rate well. High-precision relative locations define a pre-existing blind fault located 1 km below the well inside fractured and saturated carbonates where wastewater is re-injected. Seismicity begins 3 hours after the initiation of injection. The seismicity rate strictly correlates with injection curves and temporal variations of elastic and anisotropic parameters. Seismicity is induced by rapid communication of pore pressure perturbations along a high permeability fault-zone favorably oriented with respect to the local extensional stress field. Our accurate 3-D locations of 219 events (M L ≤ 2.2) detected by the local operator network after June 2006 concentrate on the pre-existing fault measuring 5.5-km along dip. Over the following 7½ years the seismicity rate correlates with short-term increases in injection pressure.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
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  • 6
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    Rapid response seismic networks in Europe: lessons learnt from the L'Aquila earthquake emergency (2011)
    In:  Annals of Geophysics
    Details
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 7
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    Rapid response to the earthquake emergency of May 2012 in the Po Plain, northern Italy (2012)
    In:  Annals of Geophysics
    Details
    Publication Date: 2020-02-12
    Keywords: 550 - Earth sciences
    Type: info:eu-repo/semantics/article
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  • 8
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    Combined approach of poroelastic and earthquake nucleation applied to the reservoir-induced seismic activity in the Val d’Agri area, Italy (2020)
    In:  Journal of Rock Mechanics and Geotechnical Engineering
    Details
    Publication Date: 2020-12-14
    Description: In this work, an approach is developed to study the seismicity associated with the impoundment and level changes of a water reservoir (reservoir induced seismicity – RIS). The proposed methodology features a combination of a semi-analytical poroelastic model with an earthquake nucleation approach based on rate-and-state frictional law. The combined approach was applied to the case of the Pertusillo Lake, located in the Val d’Agri area (Italy), whose large seasonal water level changes are believed to induce protracted micro-seismicity (local magnitude ML 〈 3). Results show that the lake impoundment in 1962 could have produced up to 0.5 bar (1 bar = 100 kPa) changes in Coulomb failure stress (ΔCFS), while the seasonal water level variation is responsible for variation up to 0.05 bar. Modeling results of the seismicity rates in 2001−2014 show that the observed earthquakes are well correlated with the modeled ΔCFS. Finally, the reason that the seismicity is only observed at southwest of the Pertusillo Lake is provided, which is likely attributed to different rock lithologies and depletion caused by significant hydrocarbon exploitation in the northeastern sector of the lake.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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  • 9
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    High-resolution controlled-source seismic tomography across the Middle Aterno basin in the epicentral area of the 2009, Mw 6.3, L’Aquila earthquake (central Apennines, Italy) (2012)
    In:  Italian Journal of Geosciences
    Details
    Publication Date: 2020-02-12
    Type: info:eu-repo/semantics/article
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  • 10
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    Source mechanisms and induced seismicity in the Val d’Agri Basin (Italy) (2023)
    In:  Geophysical Journal International
    Details
    Publication Date: 2023-08-07
    Description: We present the results from a fully unconstrained moment tensor inversion of induced seis- mic events in a complex and high seismic hazard region (Val d’Agri basin, Southern Italy). The study area hosts two well-documented cases of induced microseismicity linked to (i) a wastewater injection well of a giant oilfield (the largest in onshore Europe), and (ii) severe seasonal level changes of an artificial lake. In order to gather information on the non-double- couple components of the source and to better understand the rupture mechanisms, we analyse seismic events recorded during daily injection tests in the disposal well. The computed mo- ment tensors have significant non-double-couple components that correlate with the well-head injection pressure. The injection parameters strongly influence the rupture mechanism that can be interpreted as due to the opening/closing of a fracture network inside a fault zone of a pre-existing thrust fault. For the case of the reservoir-induced seismicity, no direct correlations are observed with the loading/unloading of the reservoir
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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