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Shear velocity structure in the Aegean area obtained by inversion of Rayleigh waves.
No full textThe purpose of this work is to derive a 3-D tomographic image of the shear wave velocity structure of the crust—uppermost mantle in the Aegean area using the group velocities of Rayleigh wave fundamental mode. The database consists of 185 regional earthquakes recorded at broad-band stations that were installed for a period of 6 month in the Aegean area within the framework of a large-scale experiment. In a previous work (Karagianni et al. 2002), an averaged group velocity has been determined using the method of frequency time analysis (FTAN) for each epicentre–station ray path and the data were used in order to determine the local group velocities for different periods over the area covered by the seismic ray paths. Taking into account additional resolution results obtained for the local group velocities, a grid of 0.5◦ was adopted for the Aegean area and a local dispersion curve was defined for each gridpoint. More than 80 local dispersion curves were finally inverted using a non-lin
A deterministic seismic hazard analysis for shallow earthquake in Greece
No full textThe maximum expected ground motion in Greece is estimated for shallow earthquakes using a deterministic seismic hazard
analysis (DSHA). In order to accomplish this analysis the input data include an homogeneous catalogue of earthquakes for the
period 426 BC–2003, a seismogenic source model with representative focal mechanisms and a set of velocity models. Because of
the discrete character of the earthquake catalogue and of errors in location of single seismic events, a smoothing algorithm is
applied to the catalogue of the main shocks to get a spatially smoothed distribution of magnitude. Based on the selected input
parameters synthetic seismograms for an upper frequency content of 1 Hz are computed on a grid of 0.2°×0.2°. The resultant
horizontal components for displacement, velocity, acceleration and DGA (Design Ground Acceleration) are mapped. The maps
which depict these results cannot be compared with previously published maps based on probabilistic methodologies as the latter
were compiled for a mean return period of 476 years. Therefore, in order to validate our deterministic analysis, the final results are
compared with PGA estimated from the maximum observed macroseismic intensity in Greece during the period 426 BC–2003.
Since the results are obtained for point sources, with the frequency content scaled with moment magnitude, some sensitivity
tests are performed to assess the influence of the finite extent of fault related to large events. Sensitivity tests are also performed to
investigate the changes in the peak ground motion quantities when varying the crustal velocity models in some seismogenic areas.
The ratios and the relative differences between the results obtained using different models are mapped and their mean value
computed. The results highlight the importance in the deterministic approach of using good and reliable velocity models.
© 2007 Elsevier B.V. All rights reserved
Non-linear arrival time tomography
No full textThe use of 1D or pseudo- 3D ray tracing techniques in linearized tomographic problems leads to solutions for which it is difficult to assess the true resolution and error distribution. For this reason, we employ a revised 3D bending algorithm (Moser et al., 1992) and show that it can be used efficiently for a non-linear inversion in a stepwise scheme. Initial paths are determined from graph theory in order to avoid local minima in bending. The importance of 3D ray tracing in inversion studies and the limitations of the standard 1D approach are demonstrated through synthetic examples. The speed of the ray tracing and the simple scaling scheme allow for an implementation in large-scale tomographic problems.JCR Journalope
Site effects in the city of Thessaloniki (Greece) estimated from acceleration data and 1D local soil profiles.
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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