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  • 1
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    In:  Geophys. Res. Lett., Kunming, China, 4, vol. 21(24), no. 1, pp. 2617-2620, pp. 2353, (ISSN: 1340-4202)
    Publication Date: 1994
    Keywords: Surface waves ; Dispersion ; GRL
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  • 2
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    In:  Geophys. J. Int., Kunming, China, 4, vol. 123, no. 1, pp. 169-182, pp. 2353, (ISSN: 1340-4202)
    Publication Date: 1995
    Keywords: EUROPROBE (Geol. and Geophys. in eastern Europe) ; Tectonics ; Inversion ; Surface waves ; Rayleigh waves ; Dispersion ; GJI
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  • 3
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    In:  Geophys. Res. Lett., Luxembourg, Conseil de l'Europe, vol. 31, no. 9, pp. 1-4, pp. L09602, (ISSN: 1340-4202)
    Publication Date: 2004
    Description: We show that relative earthquake location using double-difference methods requires an accurate knowledge of the velocity structure throughout the study region to prevent artifacts in the relative position of hypocenters. The velocity structure determines the ray paths between hypocenters and receivers. These ray paths, and the corresponding ray take-off angles at the hypocenters, determine the partial derivatives of travel time with respect to the hypocentral coordinates which form the inversion kernel that maps double-differences into hypocentral perturbations. Thus the large-scale velocity structure enters into the core of the double-difference technique. By employing a 1D layered model with sharp interfaces to perform double-difference inversion of synthetic data generated using a simple, 1D gradient model; we show that inappropriate choice of the velocity model, combined with unbalanced source-receiver distributions, can lead to significant distortion and bias in the relative hypocenter positions of closely spaced events.
    Keywords: Seismology ; Location ; Velocity depth profile ; Error analysis ; 7215 ; Seismology: ; Earthquake ; parameters ; 7230 ; Seismicity ; and ; seismotectonics ; 7260 ; Theory ; and ; modeling ; 8180 ; Tectonophysics: ; Tomography ; GRL
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  • 4
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    In:  Geophys. J. Int., Luxembourg, Conseil de l'Europe, vol. 127, no. 3, pp. 363-378, pp. L16305, (ISBN 1-86239-117-3)
    Publication Date: 1996
    Keywords: EUROPROBE (Geol. and Geophys. in eastern Europe) ; Trans-European suture zone (Tornquist-Teisseyre zone/line) ; Data analysis / ~ processing ; Inversion ; Shear waves ; Earth model, also for more shallow analyses ! ; Synthetic seismograms ; GJI
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  • 5
    Publication Date: 2018
    Description: 〈div data-abstract-type="normal"〉〈p〉The abundance of specimens of 〈span〉Ichthyosaurus〈/span〉 provides an opportunity to assess morphological variation without the limits of a small sample size. This research evaluates the variation and taxonomic utility of hindfin morphology. Two seemingly distinct morphotypes of the mesopodium occur in the genus. Morphotype 1 has three elements in the third row: metatarsal two, distal tarsal three and distal tarsal four. This is the common morphology in 〈span〉Ichthyosaurus breviceps〈/span〉, 〈span〉I. conybeari〈/span〉 and 〈span〉I. somersetensis〈/span〉. Morphotype 2 has four elements in the third row, owing to a bifurcation. This morphotype occurs in at least some specimens of each species, but it has several variations distinguished by the extent of contact of elements in the third row with the astragalus. Two specimens display a different morphotype in each fin, suggesting that the difference reflects individual variation. In 〈span〉Ichthyosaurus〈/span〉, the hindfin is taxonomically useful at the genus level, but species cannot be identified unequivocally from a well-preserved hindfin, although certain morphologies are more common in certain species than others. The large sample size filled in morphological gaps between what initially appeared to be taxonomically distinct characters. The full picture of variation would have been obscured with a small sample size. Furthermore, we have found several unusual morphologies which, in isolation, could have been mistaken for new taxa. Thus, one must be cautious when describing new species or genera on the basis of limited material, such as isolated fins and fragmentary specimens.〈/p〉〈/div〉
    Print ISSN: 0016-7568
    Electronic ISSN: 1469-5081
    Topics: Geosciences
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  • 6
    Publication Date: 2016-10-19
    Description: The accuracy of earthquake locations and their correspondence with subsurface geology depends strongly on the accuracy of the available seismic velocity model. Most modern methods to construct a velocity model for earthquake location are based on the inversion of passive source seismological data. Another approach is the integration of high-resolution geological and geophysical data to construct deterministic velocity models in which earthquake locations can be directly correlated to the geological structures. Such models have to be kinematically consistent with independent seismological data in order to provide precise hypocenter solutions. We present the Altotiberina (AT) seismic model, a three-dimensional velocity model for the Upper Tiber Valley region (Northern Apennines, Italy), constructed by combining 300 km of seismic reflection profiles, 6 deep boreholes (down to 5 km depth), detailed data from geological surveys and direct measurements of P- and S-wave velocities performed in situ and in laboratory. We assess the robustness of the AT seismic model by locating 11,713 earthquakes with a non-linear, global-search inversion method and comparing the probabilistic hypocenter solutions to those calculated in three previously published velocity models, constructed by inverting passive seismological data only. Our results demonstrate that the AT seismic model is able to provide higher-quality hypocenter locations than the previous velocity models. Earthquake locations are consistent with the subsurface geological structures and show a high degree of spatial correlation with specific lithostratigraphic units, suggesting a lithological control on the seismic activity evolution.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
    Publication Date: 2013-01-11
    Description: The accurate determination of locations and magnitudes of seismic events in a monitored region is important for many scientific, industrial and military studies and applications; for these purposes a wide variety of seismic networks are deployed throughout the world. It is crucial to know the performance of these networks not only in detecting and locating seismic events of different sizes throughout a specified source region, but also by evaluating their location errors as a function of the magnitude and source location. In this framework, we have developed a method for evaluating network performance in surface and borehole seismic monitoring. For a specified network geometry, station characteristics and a target monitoring volume, the method determines the lowest magnitude of events that the seismic network is able to detect ( M w detect ), and locate ( M w loc ) and estimates the expected location and origin time errors for a specified magnitude. Many of the features related to the seismic signal recorded at a single station are considered in this methodology, including characteristics of the seismic source, the instrument response, the ambient noise level, wave propagation in a layered, anelastic medium and uncertainties on waveform measures and the velocity model. We applied this method to two different network typologies: a local earthquake monitoring network, Irpinia Seismic Network (ISNet), installed along the Campania-Lucania Apennine chain in Southern Italy, and a hypothetic borehole network for monitoring microfractures induced during the hydrocarbon extraction process in an oil field. The method we present may be used to aid in enhancing existing networks and/or understanding their capabilities, such as for the ISNet case study, or to optimally design the network geometry in specific target regions, as for the borehole network example.
    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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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Carbohydrate Research 103 (1982), S. 129-132 
    ISSN: 0008-6215
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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