186,175 research outputs found
Primi risultati nell’analisi degli spostamenti verticali nella zona di Gemona mediante tecnica DInSAR
No full textPrimi risultati nell'analisi degli spostamenti verticali nella zona di Gemona mediante tecnica DInSAR
No full textDifferential SAR interferometry (DInSAR) is a technique monitoring large-coverage surface deformations using a stack of interferograms generated from severals complex SLC SAR images acquired over the same target area at different times. This work is focused on overview of a procedure to calculate of terrain motion velocity on highly correlated pixels. The choosen of these pixels depends on the dispersion index value D A Consecutively results derived with 18 SAR images of Gemona's area are presented
Due Differenti Approcci Per L'analisi Degli Spostamenti Verticali Mediante Tecnica Dinsar
No full textAuthor-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Sustained strain localisation and coeval brittle-ductile deformation in an exhuming low-grade shear zone: Insights from the Saih Hatat Window (NE Oman)
No full textSynkinematic phyllosilicates play a key role in controlling the rheology and the style of shear zones. At the same time, aqueous fluids released by metamorphic dehydration reactions may transiently increase pore pressure, triggering cyclic switching between brittle and ductile deformation. The Hulw Shear Zone in Oman is an exhumation-related shear zone wherein these processes can be studied. Its footwall is mostly composed of
metapelites, with a modal enrichment in phyllosilicates matched by a progressive increase in their physical interconnectivity along its internal strain gradient. Similarly, marbles in the hanging wall evolve from mylonitic to ultramylonitic toward the core of the shear zone. The Hulw Shear Zone started from peak conditions of 300–350 ◦C and 0.9–1.2 GPa, followed by the main shearing event at 350–420 ◦C and 0.6–0.9 GPa and ended at 350 ◦C, 0.3–0.4 GPa between c. 76-75 Ma. Decompression-driven fluid-gain reactions facilitated the growth of phyllosilicates, which created a pervasive and interconnected network that promoted strain localisation, causing mechanical weakening as well as the potential compartmentalized fluid cells within the mylonitic foliation. Brittle structures formed due to aqueous fluid release by metamorphic dehydration reactions, transiently increasing pore pressure and triggering brittle failure, resulting in coeval mylonitic foliation and veins. Our findings support sustained shearing promoted by synkinematic K-rich white mica and pyrophyllite growth and cyclic switching between brittle and ductile deformation conditions. The studied structures might represent a record of deep episodic tremors and slow slip events during exhumation-related tectonics in the accretionary wedge of the Oman continental lithosphere
Miocene climate cooling and aridification of Antarctica may have enhanced syn-extensional magmatism in the western Ross Sea
No full textContinental rift systems are commonly characterized by volcanism with parental basaltic magmas sourced from the mantle. Erosion of the rift shoulders and sedimentation in the adjacent basins can affect the stress and thermal fields at depth, thereby affecting partial mantle melting. However, the sensitivity of magmatic activity to such surface forcing is elusive. Geological observations from the western Ross Sea, Antarctica, suggest rift onset in the Cretaceous with a transition from wide-rifting to narrow-rifting at the boundary between the Antarctic craton and the Transantarctic Mountains. Miocene climate cooling during rifting in the western Ross Sea, in addition, leads to an abrupt decrease in sedimentation rate, synchronous to the emplacement of the McMurdo Volcanic Group. This represents the largest alkali province worldwide, extending both inland and offshore of Transantarctic Mountains and western Ross Sea, respectively. Here, we use coupled thermo-mechanical and landscape evolution numerical modeling to quantify melt production in slowly stretching rift basins due to changes in erosion/deposition rates. The model combines visco-elasto-plastic deformation of the lithosphere and underlying mantle during extension, partial rock melting, and linear hillslope diffusion of the surface topography. The parametric study covers a range of slow extension rates, crustal thicknesses, mantle potential temperatures and diffusion coefficients. Numerical simulations successfully reproduce the similar to 150-200-km-wide extension of western Ross Sea and Miocene-to-present asthenospheric melt production (McMurdo Volcanic Group). Results further show that slow rifts magmatism is highly sensitive to sediment deposition within the basin, which inhibits mantle decompression melting and delays the crustal breakup. Regional climate-driven sedimentation rate changes are thus likely to have affected the syn-rift magmatic history of the western Ross Sea, Antarctica, supporting the relevance of interactions between surface and deep-seated processes across extensional settings
Effects of asthenospheric flow and orographic precipitation on continental rifting
No full textAsthenosphere-lithosphere interactions modulated by surface processes generate outstanding topographies and sedimentary basins, but the nature of these interactions and the mechanisms through which they control the evolution of extensional tectonic settings are elusive. Basal lithospheric shearing due to plume-related mantle flow leads to extensional lithospheric rupturing and associated magmatism, rock exhumation, and topographic uplift away from the plume axis by a distance inversely correlated to the lithospheric elastic thickness. When moisturized air encounters a topographic barrier, it rises, decompresses, and saturates, leading to enhanced erosion on the windward side of the uplifted terrain. Orographic precipitation and asymmetric erosional unloading facilitate strain localization and lithospheric rupturing on the wetter and more eroded side of an extensional system. This simple analytical model is validated against thermo-mechanical numerical experiments where a rheologically stratified lithosphere above an asthenospheric plume is subject to fluvial erosion proportional to stream power during extension. Our modeling results are consistent with Paleogene mantle upwelling and flood basalts in Ethiopia synchronous to distal initiation of lithospheric stretching/rupturing in the Gulf of Aden, which progressively propagates into the Red Sea. The present-day asymmetric topography and extensional structures in the Main Ethiopian Rift may also be an effect of a Neogene-to-present orographic erosional gradient. Although inherently related to the lithosphere rheology, the evolution of continental rifts appears even more conditioned by the mantle and surface dynamics than previously thought
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
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