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Vulnerability assessment and risk mitigation: the case of Vulcano Island, Italy
No full textThe paper reports on a comprehensive vulnerability analysis based on a research work developed within the EC ENSURE Project (7FP) dealing with the assessment of different volcanic phenomena and induced mass-movements on Vulcano Island (S Italy) as a key tool for proactive efforts for multi-risk mitigation. The work is mainly focused on tephra sedimentation and lahar hazards and related physical, systemic and mitigation capacities
Submarine Slope Failures along the Northern Sicilian Continental Margin (Southern Tyrrhenian Sea) and Possible Implications for Geo-hazard
Full text linkMass wasting and downslope movements are common processes that have contributed to shape the northern
Sicilian continental margin (southern Tyrrhenian Sea) since the Late Quaternary. Nevertheless, processes
controlling their evolution are still partially unknown and a variety of geologic factors can be responsible for
their formation. In this work we present an overview of the main mass wasting features (submarine canyons,
landslides, debris flows) observed and mapped in different sectors of the northern Sicilian margin. The margin is
characterized by a narrow, steep continental shelf (1-2°) and a very irregular and steep (6-8°) upper slope. The
main aims of this work are: (1) to outline the morphology of the submarine canyons and of the related mass
failure features, (2) to describe the main geological processes that control mass failure and (3) highlight their
potential implications for the geo-hazard. The study is based on Multi Beam echosounder, Side Scan Sonar data
and seismic reflection profiles, for a depth range of 20-1500 m, and on sediment samples and scattered gravity
cores, collected to define the textural and compositional properties of the seafloor. Our study focused on the
Castellammare Gulf-San Vito Trough system, the Gulf of Palermo, the Termini-Cefalù offshore and the Ustica
offshore. In the Castellammare Gulf two main channel systems converge at the San Vito Canyon. This latter
develops northwards with a very sinuous pattern, crossing the San Vito through. In the western margin of the
Gulf, where the upper slope is very steep (12-13°) and the continental shelf is very narrow or absent, there are a
lot of short, straight, sub-parallel gullies that are only few metres deep. In this sector the gully heads are located
very close to the coastline and are associated to retrogressive slides. According to the aforesaid, downward
erosive flows appear to be the most common mechanism generating widespread slope failure inside the
Castellammare Gulf. In the Palermo Gulf a difference in slope configuration can be observed between western
and central-eastern sector. Submarine canyons are confined to the upper slope or indent the shelf-edge and enter
the Palermo intraslope basin at a depth of around 1,300 m. The canyons evolved through concurrent top-down
turbiditic processes and bottom-up retrogressive mass failures. Most of the mass failure features of the area are
related to canyon shaping processes. The western sector of the Palermo Gulf slope displays a highly dissected
substrate, showing steep to very steep gradients, that appear to favour a retrogressive evolution of the canyons.
Headward erosion processes are the main controlling factor in shaping this sector. NNE trending canyons
occurring in the central-eastern sector develop in connection with the Oreto and Eleuterio rivers, breaching the
shelf break, and show a linear to sinuous thalweg path. A similar pattern can be recognized in the eastern sector
of the Termini-Cefalù offshore. The occurrence of pockmarks and carbonate mounds also suggests the probable
role that fluid seeps play in the mass wasting processes of the area. Furthermore, the occurrence of pockmarks
and highs that probably consist of authigenic carbonates above faulted and folded strata suggests a local
relationship between structural control, fluid escape processes and mass failure. In the Ustica offshore volcanism
related features (debris avalanche, gravitational collapse of volcanic edifices) are mainly linked to neotectonic
activity and volcanism that tends to build, load and steepen the submarine slopes with time. This paper presents
a valuable high-resolution morphologic dataset of the northern Sicily continental margin, which constitutes a
reliable base for evaluating the geo-hazard potential related to slope failures in the area, through monitoring of
areas where mass movement might be forthcoming and modelling landslides consequences to develop geohazard
mitigation strategies
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