1,720,962 research outputs found
The Alps and the deep revolution against standard plate tectonics: polarized plate tectonics.
No full textThe asymmetries between W-directed (e.g. Apennines) and E- or NE- directed (e.g. Alps) subduction zones are robust features of a polarized geodynamics and they can be ascribed to the generalized westward drift of the lithosphere relative to the underlying mantle
Stability of fault plane solutions for the major N-Italy seismic events in 2012
No full textWe propose a critical analysis of themoment tensor solutions of themajor seismic events that affected northern
Italy in 2012. Inverting fullwaveforms at regional distance using the non-linear method named INPAR, we investigate
period dependent resolution that affects in particular the solutions of shallowevents. This is mainly due to
the poor resolution of Mzx and Mzy components of the seismic tensor when inverting signals whose wavelengths
significantly exceed the source depth. As a consequence, instability affects both source depth and fault plane solution
retrieval, and spurious large Compensated Linear Vector Dipole components arise. The inversion
performed at cutoff periods shorter than 20 s reveals in many cases different details of the rupture process,
which are supported by independent geodynamical arguments. Thus we conclude that inversion of full waveforms
at cutoff period as short as possible should be preferred
The lithosphere-asthenosphere system of the Periadriatic region: a geophysical perspective
No full textWe present a multiscale 3D model of the crust and upper mantle of the Periadriatic region showing how the Adriatic plate, the Northern indent of the African promontory, is involved in the Apennines, Alpine, and Dinarides subduction zones, respectively surrounding its western, northern, and eastern margins.
The model is obtained through the ensemble of cellular models expressed in terms of shear waves velocity (Vs), thickness and density of the layers, to a depth of 350 km. These physical properties are obtained by means of advanced non-linear inversion techniques, such as the "hedgehog" inversion method of group and phase velocity dispersion curves for the determination of Vs and the non-linear inversion of gravity data by means of the method GRAV3D.
The model obtained at the scale of 1 x1 is analysed along selected sections perpendicular to the orogenic complexes of the study area (Apennines, Alps, Dinarides) and it confirms the existence of deep structural asymmetries between E- and W-directed subduction zones. The asymmetry found between the almost vertical Apenninic subduction and the Alpine-Dinaric subduction, which is in turn characterized by a low dip angle, can be ascribed to an eastward mantle flow taking place in the low velocity zone (LVZ) that characterizes the top of the very shallow asthenosphere beneath the Tyrrhenian basin. The high-resolution model obtained for the Alpine region at a scale of 0.5 x0.5 enlightens the extreme variability of the crustal thickness as well the small scale heterogeneities in the upper mantle beneath the study area. The density model clearly shows that the subducting lithosphere turns out to be less dense than the surrounding mantle. A temperature model of the mantle layers is obtained by means of an advanced conversion technique of Vs to temperature that takes in account variable chemical composition and bulk water content.
The superposition of different geodynamic mechanisms in the mentioned areas is coherent with the global asym- metry of plate tectonics, evidence of polarized plate tectonics, and supports a passive origin of plate boundaries, contrary to what is usually assumed
Lithosphere density model in Italy: no hint for slab pull
No full textThe lithosphere–asthenosphere system of the Italic region in terms of shear-velocity and density distribution with depth is suitable to investigate the geodynamic context of the region. The velocity structure is obtained through nonlinear inversion of dispersion curves compiled from surface wave tomography on cells 1° × 1° and a smoothing optimization method to choose the representative cellular model, whose layering is used as fixed (a priori) information to obtain a density model by means of linear inversion of gravimetric data. Seismicity and heat flow are used as independent constraints in outlining both the crustal and the seismic lid thickness; the nonlinear moment tensor inversion of recent damaging earthquakes allows some insight in the ongoing kinematic processes. Asymmetry between west-directed (Apennines) and east-directed (Alps, Dinarides) subductions is a robust feature of the velocity model, while density model reveals that slabs are not denser than the ambient mantle, thus supplies no evidence for slab pull
An explosive component in a December 2020 Milan earthquake suggests outgassing of deeply recycled carbon
Full text linkCarbon dragged at sub-arc depths and sequestered in the asthenospheric upper mantle during cold subduction is potentially released after millions of years during the breakup of continental plates. However, it is unclear whether these deep-carbon reservoirs can be locally remobilized on shorter-term timescales. Here we reveal the fate of carbon released during cold subduction by analyzing an anomalously deep earthquake in December 2020 in the lithospheric mantle beneath Milan (Italy), above a deep-carbon reservoir previously imaged in the mantle wedge by geophysical methods. We show that the earthquake source moment tensor includes a major explosive component that we ascribe to carbon-rich melt/fluid migration along upper-mantle shear zones and rapid release of about 17,000 tons of carbon dioxide when ascending melts exit the carbonate stability field. Our results underline the importance of carbon-rich melts at active continental margins for emission budgets and suggest their potential episodic contributions to atmospheric carbon dioxide
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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