1,721,021 research outputs found
Coastal retreat and marine flooding scenario for 2100: A case study along the coast of Maddalena peninsula (southeastern Sicily)
No full textANZIDEI M., SCICCHITANO G., TARASCIO S., DE GUIDI G., MONACO C., BARRECA G., MAZZA G., SERPELLONI E. & VECCHIO A., Coastal retreat and marine flooding scenario for 2100: a case study along the coast of Maddalena Peninsula (southeastern Sicily). (IT ISSN 0391-9838, 2018). The coastal area of southeastern Sicily (Italy) is undergoing weak land subsidence, heavy coastal retreat, land flooding and exposed to severe storms associated with high-waves, also in consequence of the global sea level rise, which is expected to raise even more that 1 m by 2100 AD depending on different estimates. This value will be even larger in subsiding coasts, entailing widespread environmental changes, coastal retreat, marine flooding and loss of land, which will be subtracted to human activities. To understand the impact of rising sea level on the coast of Maddalena Peninsula, near the town of Siracusa, we realized a very high resolution Digital Terrain Model (DTM) through aerial photogrammetric surveys, obtained by Unmanned Aerial Vehicles (UAV) on which we projected the expected coastline for 2100 AD. Here we show a detailed marine flooding scenario for 2100, as generated from: i) high resolution DTM, ii) rate of land subsidence from GPS data and iii) predicted sea level projections from the IPCC AR5 reports (RCP2.6 and RCP8.5). Our analysis estimates a maximum relative sea level rise at 0.20 m and 0.65 m for 2050 AD and 2100 AD, respectively for AR 8.5 scenario. The increased sea levels will cause relevant morphological changes to the investigated coast with a maximum beach retreat of 27 m and a loss of land of 7400 m2, affecting building integrity and people safety
Quaternary and active tectonics along the Tyrrhenian coast of Sicily and Calabria
No full textAn intense tectonic activity in eastern Sicily and southern Calabria is well documented by the differential uplift of Late Quaternary coastlines and by the record of the strong historical earthquakes (1693, south-eastern Sicily; 1783 southern Calabria; 1818, Catania; 1865, Etna; 1908, Messina Strait; 1990, Augusta). The extensional belt that crosses this area is dominated by a well established WNW-ESE-oriented extensional direction. However, this area is largely lacking of any structural analysis able to define the tectonics at a more local scale. In the attempt to fill this gap of knowledge, we carried out a systematic analysis of extension joint sets. Indeed, the systematic field collection of these extensional features, coupled with an appropriate inversion technique, allows to infer the causative tectonic stress field.
Joints are defined as outcrop-scale mechanical discontinuities showing no evidence of shear motion and being originated as purely extensional fractures. Such tectonic features are one of the most common deformational structures in every tectonic environment and particularly abundant in the study area. A particular arrangement of joints, called "fracture grid-lock system", and defined as an orthogonal joint system where mutual abutting and crosscutting relationships characterize two geologically coeval joint sets, allows to infer the principal stress directions and the stress ratio.
We performed the analyses of joints only on Pleistocene deposits of Eastern Sicily and Southern Calabria. These deposits represent the infilling of Pliocene-Pleistocene basins controlled by the activity of the main fault system and consist essentially of shallow marine or transitional sediments.
Moreover we investigated only calcarenite sediments and cemented deposits, avoiding claysh and loose matrix-supported clastic sediments where the deformation is generally accomodated in a distributed way through the relative motion between the single particles. In the selection of the sites, we also took into account the possibility to clearly observe the geometric relationships among the joints. For this reason we chose curvilinear road cuts or cliffs, wide coastal erosional surfaces and quarries.
The numerical inversions show stress tensors similar at all the investigated sites. Indeed, the maximum principal stress axis σ1 is always vertical or subvertical, while the intermediate and the least axes (σ2 and σ3) lie on the horizontal plane or show low plunging values. The main direction of extension (σ3) at each site is in general agreement with the first-order regional stress field (WNW-ESE) even though some local perturbations have been recognized. These are interpreted as due to interferences between large active faults and their particular geometrical arrangement. In particular local stress deflections and stress swaps systematically occur in zones characterized by two overlapping fault segments or close to their tips
Spatial variation of crustal tectonic stress in the southern Calabrian Arc.
No full textCalabrian Arc is the area characterized by the greatest strain rate in the whole Italian peninsula (Palano, 2015). The
crustal tectonic stress of this area is highly variable and the cause lies in the interaction between large scale geodynamic
processes with the regional and local tectonic ones. We collected a dataset of 447 crustal stress indicators, published
data and original ones, with the aim of displaying the trajectories of the minimum horizontal stress throughout the study
area. The catalogue comprise two datasets. The former collects published and unpublished information relative to
Quaternary outcrop scale and regional scale structural features. We also carried out dedicated field surveys in order to
collect new data focusing on the areas lacking information. We measured about 1,400 meso-scale structural features at
39 different sites. All the collected information have been inverted with numerical techniques to obtain the associated
stress tensors. The second dataset consists 387 focal solutions all coming from published papers. The information
provided by the different authors has been homogenised by calculating the directions of T, P and B axes.
From the stress indicators we considered the direction of the least principal stress s3with plunge <20°. The catalogue
was initially elaborated as unique, then it has been subdivided in order to explore separately the stress acting in the
shallower and in the lower crust. Data were interpolated on a 0.1° stepped grid using the algorithm and software
proposed by Carafa et al.(2015). At this stage the indicators have been considered equal and no weight was assigned
during the interpolation.
In the shallower layer (0-10 km)the pattern of the Sh min clearly shows a general trend roughly E–W to ESE–WNW
oriented; in general Sh min is homogeneous and varies with an angular span of about 50°. The average direction is N116°.
In the deeper layer (10-35 km) the Sh min trend shows higher variability. The general ESE–WNW trend is slightly
recognizable and marks only relatively small sub-positions. In particular, Sh min is NE-SW in the southeastern and
southwestern parts and roughly NNW-SSE in the central eastern part of the study area. In several nodes of the grid, the
interpolated Sh min orientation from the shallow dataset is almost orthogonal to the deeper one.
Considering the stress indicators in the whole crust, the Sh min trajectories agree with the first-order tectonic stress
field being ESE-WNW and Sh min is always at high angle with respect to the major normal faults. This distribution
confirms the existence of a dominating geodynamic process active (at least) since late Quaternary. Conversely,
discriminating the Sh min at shallow and deep crustal levels some differences arise. In the shallow crust, the Sh min
trajectories are generally more coherent with the regional picture but in the deeper crust they show a higher variablility.
Such second-order deflections of the stress field are rather concentrated below 10 km depth and this seems not justified
by the role of the major faults (De Guidi et al., 2013). Probably other causes have to be find in the deeper crustal levels
where several Vp anomalies have been highlighted by seismic crustal tomography (Presti et al., 2013; Palano et al;
2015).
The approach followed in this study represents a new tool to investigate the tectonic stress and its continue spatial
variation across the southern Calabrian Arc and it also allows a better comparison with geodetic or tomographic
information
New evidence for Late Quaternary deformation of the substratum of Mt. Etna volcano (Sicily, Italy): clues indicate active crustal doming
No full textStratigraphic and morphostructural analyses have been carried out in the Mt. Etna volcanic region (eastern Sicily) to investigate in detail the deformation events that have affected the sedimentary successions forming the substratum of the volcano. In the foredeep, Quaternary submarine sedimentation ended 600 ka ago when the whole area emerged in response to homogeneous regional uplift. The irregular distribution of a stratigraphic marker, recognized through the analysis of more than 250 borehole logs, suggests that local dynamics also affected the area. We identify both compressional tectonic dynamics and volcano-related tectonic activity, and discriminate among their associated deformations. In particular, we quantify the vertical deformation component of the compressional structures (thrusts and related folds) and recognize for the first time a vertical component of deformation whose pattern clearly indicates a doming process acting at Mt. Etna. The comparison between long-term and short-term rates suggests that the doming has acted consistently over space and time through the last 600 ka and provides clues to the source of uplift. This component, defined by a specific Quaternary sedimentary horizon, has been compared with vertical deformation obtained by analytical inversion of morphological substratum data, and localizes the source at a depth of similar to 16 km, at the mantle-crust transition. This uplift may be the consequence of hydration occurring in the altered ocean-like crust
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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