1,721,008 research outputs found
Landslide inventory and rockfall risk assessment of a strategic urban area (Palermo, Sicily)
No full textThis study concerns the assessment of the rockfall risk for two strategic sectors of the Mount Pellegrino, one of the most relevant place in the city of Palermo. During the last two decades, several rockfalls affected the study area setting up a serious threat to the people, structures and infrastructures preventing the economic and social development. For these landslides a detailed GIS inventory was realized; the most dangerous rockfalls occurred within the two study sectors. In both areas we have carried out detailed field surveys and the geo-mechanical characterization of the rock slopes. These analyses allowed to define the rock mass parameters, the set of discontinuities and the kinematics. The back analyses for the past events were conducted permitting to define the blocks trajectories using a numerical model for rockfall simulation. Through this procedure the hazardous areas have been identified and the map of the landslide risk was produced considering the possible spread of the blocks both on land and at sea. The results were exploited to compare this map with the existent map in the framework of the Sicilian Master Plan for hydrogeological risk (PAI), showing that the new risk areas are larger than those previously mapped
ANALISI DEI MECCANISMI DI RIATTIVAZIONE DI UN’AREA IN FRANA NEL BACINO DEL FIUME IMERA SETTENTRIONALE
No full textAl fine di valutare le condizioni limite per la stabilità di un pendio in frana, sono state svolte delle analisi di stabilità all’equilibrio limite 2D e 3D in un’area ubicata nel bacino del fiume Imera Settentrionale (Sicilia). Tali analisi hanno permesso di ricostruire un modello geologico e geotecnico ottimale, di individuare il livello piezometrico che ha determinato le condizioni di instabilità e di definire i parametri operativi di resistenza a taglio dei terreni. Le recenti riattivazioni dei meccanismi di frana hanno fornito elementi che hanno permesso di validare in particolare i risultati delle analisi numeriche 3D. I risultati ottenuti hanno anche evidenziato che il metodo di analisi tridimensionale costituisce un valido strumento di analisi, capace di prevedere l’estensione areale dei dissesti e di fornire una migliore stima della resistenza a taglio operativa dei terreni, soprattutto nei casi in cui la morfologia del pendio è complessa e la direzione degli spostamenti non è omogenea
Relationships between a new slope morphometric index and calanchi erosion in northen Sicily, Italy
No full textThe Italian badlands, or “calanchi”, are common landforms in Mediterranean areas including central and
southern Italy. Calanchi landforms may be compared to small hydrographic basins. These landforms are
characterised by dense, hierarchical and rapidly evolving drainage systems carved into steep clayey slopes
and by a sharply alternating pattern of furrows and narrow, generally sharp crests.
This work presents a study of morphometric characteristics and a statistical analysis for two sites in northern
Sicily (Italy), on outcrops of silty-clay deposits affected by active erosion processes, which give this area a typical
calanchi landscape. In particular, factors closely linked to the characteristics of the hydrographic network and
slope morphometry were considered and analysed. The initial geometry of the slopes was reconstructed and
statistically compared with that of the current calanchi slopes including the drainage network.
A new morphometric index (Morphometric Slope Index, MSI) was defined to represent the initial slope geometry
as awhole. This indexwas found to be effective in defining the structure of hydrographic networks, summarising
the characteristics and type of slope evolution, and quantifying the rate of soil erosion. The rate was
determined based on both linear (gully erosion) and areal (landslides, sheet and rill erosion) morphogenetic
processes, and our analysis based on MSI indicates the dominance of areal erosion. MSI could also be used for
basins larger than calanchi to represent the characteristics of geomorphic processes
Exploring the geomorphological adequacy of the landslide susceptibility maps. A test for different types of landslides in the Bidente river basin (northern Italy)
Full text linkLandslide susceptibility modelling is a crucial tool for implementing effective strategies in landslide risk mitigation. A plethora of statistical methods is available for generating accurate prediction images; however, the reliability of these models in terms of geomorphological adequacy is often overlooked by scholars. This critical flaw may result in concealed prediction errors, undermining the trustworthiness of the obtained maps. A key aspect of evaluating the geomorphological soundness of these models lies in factor analysis, specifically considering the correlation of explanatory variables with the final susceptibility score rather than solely focusing on their impact on model accuracy. This study delves into research conducted in the Bidente river basin (Italy) that analyes results obtained from slide, flow, and complex susceptibility models using Weight of Evidence (WoE) and Multivariate Adaptive Regression Splines (MARS) statistical methods. The research critically examines each factor class's role in defining susceptibility scores for different landslide typologies. The comparison between susceptibility maps generated by WoE and MARS for each typology (slide = 0.78; flow = 0.85; complex: 0.79) (slide = 0.78; flow = 0.85; complex: 0.79)reveals good to excellent prediction skill, with MARS demonstrating a 5 % higher performance index. The study emphasises the importance of spatial relationships between variables and landslide occurrences, highlighting that individual classes of variables influence the final susceptibility score based on their combined role with other predictor classes. In particular, in this study, results highlight that lithotecnical and landform classification classes delimit the landslide domain, while topographic attributes (steepness, curvatures, SPI and TWI) modulate the score inside. The proposed approach offers insights into investigating the geomorphological adequacy of landslide prediction images, emphasising the significance of factor analysis in evaluating model reliability and uncovering potential errors in susceptibility maps
Preliminary results of a geomorphological and DInSAR characterization of a recently identified Deep-Seated Gravitational Slope Deformation in Sicily (Southern Italy)
No full textThe study is part of a larger project that involves the analysis of recently identified Deep-Seated Gravitational Slope Deformation (DSGSD) in Sicily which have been sub-divided according to the geological framework in light of the new geological data about the regional setting. Here are presented the first results of a multidisciplinary study of a DSGSD recently identify in Mount San Calogero area (Northern Sicily). The study was performed by means of different approaches including conventional methods (field surveys) and the Differential Interferometry Synthetic Aperture Radar (DInSAR) technique. The geological and geomorphological analyses were carried out to investigate slopes dynamic, and DInSAR analysis were integrated to obtain, for the first time in this area, displacement rates of the DSGSD. The identified deformation patterns show the effective movement of homogeneous rock mass that constitutes the Mount San Calogero, characterized by the gravitational morphostructures and evidence of slopes deformation, as well as the shallow landslides detected in the foothill area. Furthermore, the distribution of the Persistent Scatterers (PS) points shows a clear convergence with the main tectonic lineaments of the area, thereby emphasizing the role of the structural setting in the DSGSD's development
Malta and Sicily Joined by Geoheritage Enhancement and Geotourism within the Framework of Land Management and Development
Full text linkMalta and Sicily, which lie at the centre of the Mediterranean Sea, share a long history and have unique geological and geomorphological features which make them attractive destinations for geotourism. In the framework of an international research project, a study for the identification, selection and assessment of the rich geological heritage of Malta and Sicily was carried out, aiming to create a geosite network between these islands. Based on the experience and outputs achieved in previous investigations on geoheritage assessment carried out in various morpho-climatic contexts, an integrated methodology was applied for the selection, numerical assessment and ranking of geosites. The selection phase was based on three main criteria—scientific, additional and use values—and led to the establishment of a list of 42 geosites (20 in Malta and 22 in Sicily). Besides being spectacular and attractive for tourists, these sites represent the main geomorphological contexts and the various stages of regional morphogenesis of the study areas. The sites selected were assessed quantitatively and ranked according to management and tourism criteria. The results provide both the necessary basic knowledge for joint conservation actions and policies in Malta and Sicily and the elements for creating a link between Malta and Sicily through geoheritage appraisal and tourism development
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
Susceptibility analysis for seismically-induced landslides: application to the 2001 earthquakes in El Salvador (C.A.)
Full text linkThe geodynamic context in which El Salvador is located, made of a convergent structure characterized by the interaction among six different plates, together with the lithological characteristics of the outcropping rocks and soils (mainly corresponding to deeply weathered acid pyroclastites, basic effusive rocks and volcanic ashes), are responsible for the very high seismically- induced landslide susceptibility of the country. These predisposing factors were decisive on the occurrence of thousands of seismically-induced landslides caused by two huge earthquakes on 13th January and 13th February 2001, which triggered thousands of landslides in the country. In particular, the February event (6.6M, onshore and intraplate at a depth of 10 km) triggered 5,371 landslides in an area of around 300km2. These gravitational phenomena took the form of debris slides, earth slides and debris flows and affected several inhabited areas damaging infrastructures and crops and causing, respectively 844 and 315 fatalities.
Thanks to aerial photos taken soon after the days following both the two earthquakes and made available by the CNR (Centro Nacional de Registros - Instituto Geográfico y del Catastro Nacional), associated landslide maps have been prepared, where each phenomenon is represented by a landslide polygon and its LIP (Landslide Identification Point), located in the crown of the landslide. In particular, static landslide susceptibility models were prepared for the Ilopango (1594 landslides in an area of around 40km2) and the San Vicente (1602 landslides in an area of around 108 km2) sectors, by regressing the spatial distribution of the 13th February seismically-induced landslides on a set of explanatory variables obtained by a geologic map and a 10m pixel DTM (Digital Terrain Model). At the same time, shaking-dependent models were prepared by including also PGA (Peak Ground Acceleration) and the epicentral distance (ED) among the predictors.
For both the two areas a marked increase of performance was observed (AUC from 0.70 to 0.75, for Ilopango, from 0.73 to 0.77, for San Vicente) from the static to the shaking-dependent models, highlighting the role of the seismic acceleration in the triggering of the landslides both in activating the susceptible sites and in lowering the score threshold for slope failures occurrences. Besides, for the Ilopango sector, a rainfall-induced susceptibility model was also prepared, exploiting a landslide inventory available for the 2009 IDA/12E storm events. The obtained score was then
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combined with PGA and ED to predict the spatial distribution of the seismically induced landslides, obtaining a higher performance than the relative basic model (AUC = 0.75).
The results obtained from the research demonstrate suggest the possibility to couple the susceptibility scores obtained from static modelling to the expected mechanical shaking for the seismically-induced susceptibility assessment.
The whole modelling was carried out by applying MARS (Multivariate Adaptive Regression Splines) analysis through RStudio and SAGA GIS freeware software
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
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