1,720,988 research outputs found
Evidenze di strutture compressive triassico-giurassiche lungo il margine settentrionale del plateau somalo (Etiopia).
No full textEvidenze di tettonica recente ed attiva nel settore esterno sepolto dell'Appennino centrale abruzzese
No full textStyle of faulting and drainage pattern along the Somalian plateau escarpment at the southern Afar margin (Ethiopia) [Stile deformativo e reticolo idrografico lungo la scarpata del Plateau Somalo al margine meridionale dell’Afar (Etiopia)]
No full textAn integrated structural and geomorphologic study along the Somalian Plateau escarpment at the southern Afar margin (Dire Dawa area, Ethiopia), provides insights into the rift geometry, timing and evolution of this sector of the East Africa Rift system. Late Triassic-Jurassic sandstones and carbonate sequences lie in nonconformity over the pre-Cambrian metamorphic basement and are in turn disconformably covered by Early Cretaceous continental and transitional sandstones and conglomerates. After another disconformity a thick sequence of Flood Basalt was deposited during the Oligocene and today crop out close to the margin of the Rift at an elevation of about 3500 m in the Somalian Plateau. Rift architecture in the study area is characterized by faulted blocks tilting away from the Afar Depression «domino-style faulting», as already described by MORTON & BLACK (1975). Major faults are ca. E-W oriented and show high-angle geometry. Kinematic indicators measured along the fault planes commonly show a slight left lateral component providing a ca. NNWSSE direction of extension. Faulted monoclines composed of footwall anticline-hanging-wall syncline pairs are observed adjacent to many of the block-bounding and intra-block faults. We interpret this structural style to have formed in response to fault-propagation folding in extensional regime. The drainage pattern in the study area is strongly influenced by the main E-W trending faults and by the NNW-SSE system of fractures and doleritic dikes emplaced during the Oligocene volcanic event. Two main stages of fault activation can be recognised in the area. In fact, the faulted blocks, although usually quite dissected, sometimes have a flat top ridge preserving the remain of a former planation surface, most probably a huge pediment that connected the main escarpment to the Afar. This pediment erase some of the faults and in the distal area is covered by Early-Middle Pleistocene Afar flood basalts. After the modelling of the pediment that also cancelled the previous drainage network, a new phase of fault activity is documented. An even older drainage has been recognised in the Plateau area, where broad paleovalleys cut for over 1400 m below the original plateau in the area which separated the Afar depression from the Somalian lowlands. Originally, they were alimented from the «Afar sector» (i.e., from the north) most probably as a consequence of the upwarping that followed the emplacement of the Trap, and evolved as superimposed rivers. The northward drainage is therefore the result of river reversion as a consequence of the down-faulting associated to the rift activation and evolution. These evidence suggest that the emplacement of the Trap occurred at low elevation and was followed by upwarping and much later by rifting processes and down-faulting
The CARG Project contribution to seismic hazard studies: The "gran Sasso d'Italia" sheet in the light of the L'Aquila eartquake (April 6, 2009)
No full textAfter the 6 April 2009 L'Aquila seismic event detailed geological and geophysical investigations produced a great amount of new information about the active faults in the L'Aquila-Gran Sasso area. A few years before the earthquake the area had been investigated for the 1:50.000 Geological Mapping CARG Project and this paper is aimed to underline the contribute provided by the geological maps in order to address detailed studies on seismic hazard in Italy. The 1:50.000 scale Sheet 349 "Gran Sasso d'Italia" has been investigated and realized taking carefully into account the Quaternary fault activity since a wide literature already existed about recent activity of many fault systems of the area. We introduced the category of "Faults with Quaternary activity" classified following detailed structural, sedimentological/ stratigraphical, chronological and, at places, paleoseismological investigations. In particular, Quaternary activity was addressed to the "Monte Stabiata Fault", probably reactivated during the L'Aquila seismic sequence (e.g., BONCIO et alii, 2010), and even described as active during the late Pleistocene. Therefore, the 1:50.000 scale geological maps of the CARG project may provide helpful and detailed information about the presence of Quaternary structures and their relationship with pre-existing structures (e.g., pre-Quaternary thrusts and normal faults) giving a first step contribution to - warmly recommended - dedicated studies for seismic hazard evaluation
Stile deformativo e reticolo idrografico lungo la scarpata del Plateau Somalo al margine meridionale dell'Afar
No full textGeometry and kinematics of folding in the outer zones of the Central Apennines: The role of Jurassic normal faults [Geometria e cinematica delle anticlinali dell'Appennino centrale esterno: il ruolo delle faglie dirette giurassiche]
No full textThe outer zones of the Central Apennines are characterized by arcuate thrusts and related NE-verging folds that affect a ca. 2000 m thick Mesozoic-Neogene sedimentary succession. The base of the succession is represented by a massive 800 m thick platform carbo- nate unit of Early Liassic age (Calcare Massiccio Fm.), that grades upwards into well-bedded pelagic carbonates, marls and silicicla- stics. The Jurassic portion of the succession displays thickness and facies variations, that are controlled by synsedimentary normal faults: these dismembered the Early Liassic carbonate platform into differently subsiding seamounts and troughs.
The onset of Neogene orogenic deformation was responsible for the contraction of the sedimentary succession. Detailed analysys of some anticlines reveals the occurrence of high-angle thrusts within the Calcare Massiccio Fm., whose displacements are accommodated by folding within the overlying pelagic succession. Thrust-related folding was locally influenced by the occurrence of Jurassic normal faults that, where present, inhibited thrust propagation toward the foreland. Folding at the expenses of Jurassic normal faults therefore results in structures that differ significantly in geometry and kine- matics from those developed across a layer-cake stratigraphic tem- plate
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
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