1,720,961 research outputs found
Structure and rheology of lithosphere in Italy and surrounding
No full textWe define the structure and rheology of the lithosphere in Italy and surrounding, combining the cellular velocity models derived from nonlinear tomographic inversion with the distribution vs. depth of hypocentres to assess the brittle properties of the Earth’s crust. We average, over cells sized 1×1 degree, the mechanical properties of the uppermost 60 km of the Earth, along with seismicity, grouping hypocentral depths in 4-km intervals. For most of the cells, the earthquake energy is concentrated in the upper crust (4–12 km). For some regions, where orogenic processes occur, the release of earthquake energy is shallower and limited to the uppermost 10 km of the crust. Ambiguities in the structural models are minimized considering the hypocentral distribution, mainly to define the location of the Moho boundary, when its identification, based on shear-wave velocities, is not straight- forward
Surface waves tomography and non-linear inversion in the southeast Carpathians.
No full textA set of shear-wave velocity models of the lithosphere–asthenosphere system in the southeast Carpathians is determined by the non-linear inversion of surface wave group velocity data, obtained from a tomographic analysis. The local dispersion curves are assembled for the period range 7–150 s, combining regional group velocity measurements and published global Rayleigh wave dispersion data. The resolution of the tomography data is improved using a priori information about the shallow crustal velocity structure. The lithosphere–asthenosphere velocity structure is reliably reconstructed to depths of about 250 km for 27 cells with size 1◦ ×1◦. The adopted non-linear inversion method computes a set of acceptable velocity models for each cell. Local smoothness optimization (LSO) is applied to select the representative cellular structures and the three-dimensional shear-wave velocity model of the studied region is assembled. Interpretation of the obtained structure shows that the thickness of the lithosphere in the region varies from about 90 km to 170 km and the asthenosphere can be as deep as about 150 km. Mantle seismicity concentrates where the high-velocity lid is detected just below the Moho. The obtained results are in agreement with recent seismic refraction, receiver function, and travel time P-wave tomography investigations in the region. The similarity among the results obtained from different kinds of structural investigations (including the present work) highlights some new features of the lithosphere–asthenosphere system in southeast Carpathians, such as the relatively thin crust under Transylvania basin and in the Vrancea zone
Upper mantle flow in the western Mediterranean
No full textTwo cross-sections of the western Mediterranean Neogene-to-present back-arc basin are presented, in which geological and geophysical data of the TRANSMED Project are tied to a new shear-wave tomography. Major results are i) the presence of a well stratified upper mantle beneath the older African continent, with a marked low-velocity layer between 130–200 km of depth; ii) the dilution of this layer within the younger western Mediterranean back-arc basin to the north, and iii) the easterly raising of a shallower low-velocity layer from about 140 km to about 30 km in the Tyrrhenian active part of the back-arc basin. These findings suggest upper mantle circulation in the western Mediterranean back-arc basin, mostly easterly-directed and affecting the boundary between upper asthenosphere (LVZ) and lower asthenosphere, which undulates between about 180 km and 280 km
Modelling of earthquake-induced tsunami in the Eastern Mediterranean Region
No full textA number of tsunamigenic zones in the Eastern Mediterranean region were investigated. Historically, the strongest tsunami waves are excited in the Hellenic and Cyprus arcs, the Aegean Sea and the Levantine coast. We modelled the generation of tsunami specifying the epicenter, the focal mechanism, and the maximum of the observed magnitude for each considered tsunamigenic zone. Our approach is based on the numerical simulations of tsunami waves, performed by the code UBO-TSUFD, developed in the University of Bologna. Initial displacement of the sea floor is calculated in accordance with Okadàs formulas. We focused our discussion on the tsunami impact on the coasts of Karpathos, Cyprus and Levantine countries. Tsunami parameters are computed for each scenario and results are used to build maps of the computed maximum tsunami heights. Synthetic mareograms are simulated for several points near some important coastal cities of the study area
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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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