1,720,955 research outputs found
New perspectives on the analysis of active fluid seepages in offshore Sicily
Get PDFThe analysis of active fluid seepages in the Sicily offshore, allows to differentiate processes that generate seabed structures (mounds and pockmarks) from buried structures (active fluid seepage, pressurized reservoirs, and gas chimneys). This distinction could be useful to assess the slope instability and the explosive potential in relation to the different physiographic environment and morphobathymetry and then the preparatory and predisposing factor of the areas to ground instability.
Seismic data acquire in different OGS, CNR and University of Palermo surveys in the Sicily Channel and Gulf of Palermo show numerous marker reflectors related to gas accumulation: bright spots (positive amplitude anomalies caused by gas and water accumulation), flat spots (horizontal seismic reflections attributed to an interface between two fluids), and Bottom Simulating Reflectors both along fluid migration paths and within shallow confined reservoirs.
The evaluation of the role of each parameter will be performed through Sensitivity Analysis. The data will be processed with geotechnical models to evaluate the stability threshold of continental slopes (Factor Of Safety) in each case study and the limit pressure levels of reservoirs and gas chimneys, in relation to geomechanical variables (e.g., intergranular cohesion, internal friction angle, undrained shear strength, etc.) on the basis of which a fragile response of the geological volume can be expected. For example, a gas chimney with height of 1 m and Pcrit ≥ 15 kPa within a sedimentary
body with internal friction angle φ of 25° at 45 mbsf may generate a seafloor shear failure.
All the results regarding this morphological and stratigraphic study of the structures linked to fluid escapes and the experimental approach of the geo-mechanical study of the process will be summarized in a table representing all the fluid escapes structures
Possible correlation between pockmarks and gravitative instabilities in Palermo Gulf
Get PDFPockmarks are negative seabed structures that, like mounds, represent the surface expression of fluid migration pathways. Their physiographic variability is highly heterogeneous, as pockmarks are found in a wide range of geological settings. In the specific case of the Gulf of Palermo, they are located on the continental slope at depths ranging between 230 and 390 m bsl. The distinctiveness of the pockmark field in this study, which spans approximately 2.3 km2, lies in its proximity to the coastline (≈ 5.8 km), its association with neotectonic lineaments, and its connection to the heads of canyons. Pockmarks exhibit diameters ranging from 90 to 320 m, with depths between 10 and 30 m.
In continuity with the studies proposed so far, the study focuses on the analysis of acoustic and seismic geophysical data acquired in the Gulf of Palermo by the marine geology group of DISTEM. The analysis of seismic profiles allowed the identification of the acoustic basement and the fluid migration pathways, which are associated (though not exclusively) with normal faults located in Palermo offshore. Based on the literature data, the type of fluids rising corresponds to continental fresh water. So, the activity of the pockmarks is not continuous but intermittent, linked to the recharge and subsequent pressurization of fluids connected to the recharge of the continental aquifer through meteorological events.
The integration of seismic profile with morphobathymetric data has revealed a weak layer, interpreted as such by its acoustic facies, at the base of landslide scars. This layer intersects the underlying fluid migration pathways associated with the pockmarks. Consequently, the identification of the areas and volumes of sediments weakened by fluid emission qualitative models regarding future retrogressive evolution of these areas. The analysis of the seismic profiles allowed the identification of a chaotic sediment deposit of about 5.75 million m3 along a landslide scar, near to the pockmark field.
In order to validate the evolutionary model proposed for the study area the approach proposed by Nian et al. (2022), which employs a geotechnical model to analyze the equilibrium of a submarine slope, has been applied. The critical equilibrium is assessed by correlating the weight of the unstable block, fluid pressure, and shear force acting along the rupture surface.
The extensive bibliographic research of geomechanical parameters and the measure of geometric parameters on seismic profile allowed the application of the Nian formula.
Evaluating the instability of a submarine slope is very important for coastal risk studies. The case study of the pockmarks in the offshore of the Gulf of Palermo, where a tight connection exists between continental and marine processes (rainfall events and the upward movement of pressurized fluids), is particularly significant in the context of climate change impact studies
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Fluid escape processes studied in Palermo offshore (NW Sicily). Quantitative analysis and modelling analysis of the factor of safety (FOS) of a submarine slope.
No full textThis study analyzes a submarine sector of Palermo offshore where the multiple cause-effect relationship between pockmarks and submarine landslides are studied by mean Multi Beam Echo Sounder (MBES) morphobathymetric data. This sector is characterized by freshwater continental origin pockmarks whose activity can be considered intermittent as associated with the recharge of the continental aquifer through meteorological events (Pennino et al., 2014).
The integration of MBES data and Sparker seismic profiles allowed us to obtain quantitative measurements of: 1) thicknesses, areas and volumes of sedimentary body altered by upward migration of pressurized fluids; 2) the presence of preferential sliding surfaces (e.g. weak layers) likely responsible of pockmark-associated landslides; 3) tectonic alignments linked to recent geological structures (predominantly N-S oriented) along which the fluids escape structures are detected.
We investigated the possibility that in the nearness of pockmark convergent reflectors, the pressurized fluids caused the loss cohesion resulting in sediments prone to movement. In the case of Palermo offshore, this hypothesis is strengthened by favorable boundary conditions such as: high slope values of the area, surrounding landslides and ongoing fluid escape processes.
The identification of areas and volumes of altered sediments, together with a critical review of literature, allowed us to develop a qualitative model regarding the potential future retrogressive evolution of these areas and, also the computation of the pockmark related Factor of Safety (FOS, Noda et al., 2013; Sultan et al., 2004). Preliminary results highlight that the pore overpressure, in intra-pockmark area, strongly influence the equilibrium of the slope and, thus, can be considered as a predisposing factor for submarine gravitational processes. Moreover, the identification of potential landslide volume could allow to investigate possible landslide triggered - tsunami waves hazard scenario
- …
