ALBERT

Description: Palermo is a populous city situated on the Northern coast of Sicily, bordered by the Tyrrhenian Basin. This central part of the Mediterranean Sea features dramatic bathymetry, numerous subaqueous landslides, and is also the epicentre to many subaqueous earthquakes. As such, the region is an area prone to tsunamis. This investigation uses the Cornell Multi-Grid Coupled Tsunami (COMCOT) tsunami modelling package to simulate five near-field landslides, and five near-field earthquakes regarded as worst-case credible scenarios to Palermo. The seismic simulations produced waves on a very small scale, the largest being ∼5 cm at its maximum height, and none of the earthquake-generated tsunami waves produced any measurable inundation. The landslide simulations produced larger waves ranging from 1.9 - 12 m in maximum height, two of which inundation in areas surrounding the Port of Palermo. Sensitivity analysis identified that fault width and dislocation as well as landslide specific gravity did have significant influence over maximum wave height, inundation, and maximum run-up wave height. There are methodological issues limiting the extent to which this study forms a comprehensive tsunami hazard assessment of Palermo, such as gaps in bathymetric data, computational restrictions and lack of a probabilistic element. These issues are counteracted by the fact that this study does serve as a robust first step in identifying that landslides in the region may produce larger tsunami waves than earthquakes, and that the directionality of mass movement is critical in landslide-driven tsunami propagation in the Southern Tyrrhenian region.

Description: We present the results of an integrated geomorphological and seismo-stratigraphic study based on high resolution marine data acquired in the north-western Sicilian continental margin. We document for the first time five contourite drifts (marked as EM1a, EM2b, EM2, EM3a, and EM3b), located in the continental slope at depths between ca. 400 and 1500 m. EM1a,b have been interpreted as elongated mounded drifts. EM1a,b are ca. 3 km long, 1.3 km wide, and have a maximum thickness of 36 m in their center that thins northwards, while EM1b is smaller with a thickness up to 24 m. They are internally characterized by mounded seismic packages dominated by continuous and parallel reflectors. EM2 is located in the upper slope at a depth of ca. 1470 m, and it is ca. 9.3 km long, more than 3.9 km wide, and has a maximum thickness of ca. 65 m. It consists of an internal aggradational stacking pattern with elongated mounded packages of continuous, moderate to high amplitude seismic reflectors. EM2 is internally composed by a mix of contourite deposits (Holocene) interbedded with turbiditic and/or mass flow deposits. EM1a,b and EM2 are deposited at the top of an erosional truncation aged at 11.5 ka, so they mostly formed during the Holocene. EM3a,b are ca. 16 km long, more than 6.7 km wide, and have a thickness up to 350 m. Both EM2 and EM3a,b have been interpreted as sheeted drift due to their morphology and seismic features. The spatial distribution of the contourite drifts suggests that the drifts are likely generated by the interaction of the LIW, and deep Tyrrhenian water (TDW) on the seafloor, playing an important role in the shaping this continental margin since the late Pleistocene-Holocene. The results may help to understand the deep oceanic processes affecting the north-western Sicilian continental margin.

Description: The Maltese Islands, located in the central Mediterranean Sea, are intersected by two normal fault systems associated with continental rifting to the south. Due to a lack of evidence for offshore displacement and insignificant historical seismicity, the systems are thought to be inactive and the rift-related deformation is believed to have ceased. In this study we integrate aerial, marine and onshore geological, geophysical and geochemical data from the Maltese Islands to demonstrate that the majority of faults offshore the archipelago underwent extensional to transtensional deformation during the last 20 ka. We also document an active fluid flow system responsible for degassing of CH4 and CO2. The gases migrate through carbonate bedrock and overlying sedimentary layers via focused pathways, such as faults and pipe structures, and possibly via diffuse pathways, such as fractures. Where the gases seep offshore, they form pockmarks and rise through the water column into the atmosphere. Gas migration and seepage implies that the onshore and offshore faults systems are permeable and that they were active recently and simultaneously. The latter can be explained by a transtensional system involving two right-stepping, right-lateral NW-SE trending faults, either binding a pull-apart basin between the islands of Malta and Gozo or associated with minor connecting antitethic structures. Such a configuration may be responsible for the generation or reactivation of faults onshore and offshore the Maltese Islands, and fits into the modern divergent strain-stress regime inferred from geodetic data.

Description: The tsunami hazard for the Maltese Islands is poorly defined, and historic records are available for only two recent events. Most of the population and touristic infrastructure of the archipelago is concentrated along the eastern low-lying coastline, which is exposed to tsunamis from near-field and far-field sources. In this study we present a scenario-based tsunami inundation study to assess the impact of potential significant cases. We simulated four scenarios—two submarine landslide sources (outer Malta Plateau slide and Gela Basin slide) and two earthquake sources mimicking events comparable to the 365 A.D. western Hellenic Arc event and the 1693 south-east of Sicily event. We find that all scenarios cause inundation in densely populated low-lying bays or rias of Mellieha Bay, Xemxija, Salini, Gzira, Msida, Marsaskala, St Thomas Bay, Marsaxlokk and Birzebbuga. The largest inundation extents and flow depths (〉 10 m) are produced by the two landslide sources and the western Hellenic Arc earthquake. Of interest is the role of the Malta Escarpment and Sicily in amplifying and reflecting tsunami waves, and in generating consistent hot spots along the eastern coastline of Malta.

Description: Highlights • We analyse seismic stratigraphy of post-Messinian succession in west Ionian Basin. • Termination of Messinian salinity crisis consisted of a single-stage Zanclean flood. • Megaflood followed a sea level drawdown of 1900 m in eastern Mediterranean. • Fine, well-sorted sediments are predicted in the thicker sections of flood deposit. • NW Ionian Basin hosts evidence of episodic slope instability after 1.8 Ma. Abstract The Messinian salinity crisis was an extraordinary event that resulted in the deposition of kilometre-thick evaporite sequences in the Mediterranean Sea after the latter became disconnected from the world's oceans. The return to fully and stable marine conditions at the end of the crisis is still subject to debate. Three main hypotheses, based on geophysical and borehole data, onshore outcrops and climate simulations, have been put forward. These include a single-stage catastrophic flood, a two-step reflooding scenario, and an overspill of Paratethyan water followed by Atlantic inflow. In this study, two research questions are addressed: (i) Which event marked the termination of the Messinian salinity crisis? (ii) What was the sea level in the eastern Mediterranean Sea during this event? Geophysical data from the western Ionian Basin are integrated with numerical simulations to infer that the termination of the crisis consisted of a single-stage megaflood following a sea level drawdown of 1900 m. This megaflood deposited an extensive sedimentary body with a chaotic to transparent seismic signature at the base of the Malta Escarpment. Fine, well-sorted sediments are predicted to have been deposited within the thicker sections of the flood deposit, whereas a more variable distribution of coarser sediments is expected elsewhere. The north-western Ionian Basin hosts evidence of episodic post-Messinian salinity crisis slope instability events in the last ~1.8 Ma. The largest of these emplaced a 〉200 km3 deposit and is associated with failure of the head of Noto Canyon (offshore SE Sicily). Apart from unravelling the final phase of the Messinian salinity crisis and the ensuing stratigraphic evolution of the western Ionian Basin, our results are also relevant to better understand megafloods, which are some of the most catastrophic geological processes on Earth and Mars.

Description: Shallow seabed depressions attributed to focused fluid seepage, known as pockmarks, have been documented in all continental margins. In this study we demonstrate how pockmark formation can be the result of a combination of multiple factors – fluid type, overpressures, seafloor sediment type, stratigraphy, and bottom currents. We integrate multibeam echosounder and seismic reflection data, sediment cores and pore water samples, with numerical models of groundwater and gas hydrates, from the Canterbury Margin (off New Zealand). More than 6800 surface pockmarks, reaching densities of 100 per km2, and an undefined number of buried pockmarks, are identified in the middle to outer shelf and lower continental slope. Fluid conduits across the shelf and slope include shallow to deep chimneys/pipes. Methane with a biogenic and/or thermogenic origin is the main fluid forming flow and escape features, although saline and freshened groundwaters may also be seeping across the slope. The main drivers of fluid flow and seepage are overpressure across the slope generated by sediment loading and thin sediment overburden above the overpressured interval in the outer shelf. Other processes (e.g. methane generation and flow, a reduction in hydrostatic pressure due to sea-level lowering) may also account for fluid flow and seepage features, particularly across the shelf. Pockmark occurrence coincides with muddy sediments at the seafloor, whereas their planform is elongated by bottom currents.

Description: Graham Bank is a dominant physiographic element of the NW Sicily Channel (central Mediterranean Sea), affected in the last 100 years by numerous well-documented volcanic eruptions.We present the first results of a geomorphological study where the Graham Bank region in the depth interval 7–350 m was mapped for the first time with multi-beam echosounder and high-resolution seismic and multi-channel seismic reflection profiles. We describe in high resolution the detailed geomorphological features of Graham Bank, and how the superficial expression of different process and dynamics occurring in the sub-seafloor evidence volcanic and tectonic controls on seafloor morphology across a relatively small area. The north-eastern part of the study area is dominated by seamounts with heights ranging from 97 to 152mand auxiliary small cones, reaching heights of 2–10 m, on thewhole forming a hummocky surface. In this region, fluid seepages are an important expression of the volcanic processes affecting the study area. Thewestern region comprises a flat seafloor covered by Upper Pleistocene-Holocene outer shelf sedimentary deposits; here aligned mounds and pockmarks are predominantly orientedNW–SE orNNW-SSE, running parallel to the main structural trend of the Sicily Channel. The pockmarks have sub-circular planform shapes and U-shaped cross-section and different depths and mean axis lengths. Numerous Mass Transport Deposits (MTDs) are distributed across the study area. Graham Bank is 45 km from the coast of Sicily and is intersected by submarine cables. Consequently, the mapped volcanic seamounts, pockmarks and MTDs could pose a significant economic risk to the submarine cables.

Description: Published

Description: 375-389

Description: 2V. Struttura e sistema di alimentazione dei vulcani

Description: 2TR. Ricostruzione e modellazione della struttura crostale

Description: JCR Journal

Description: The Maltese Islands, located in the central Mediterranean Sea, are intersected by two normal fault systems associated with continental rifting to the south. Due to a lack of evidence for offshore displacement and insignificant historical seismicity, the systems are thought to be inactive and the rift-related deformation is believed to have ceased. In this study we integrate aerial, marine and onshore geological, geophysical and geochemical data from the Maltese Islands to demonstrate that the majority of faults offshore the archipelago underwent extensional to transtensional deformation during the last 20 ka. We also document an active fluid flow system responsible for degassing of CH4 and CO2. The gases migrate through carbonate bedrock and overlying sedimentary layers via focused pathways, such as faults and pipe structures, and possibly via diffuse pathways, such as fractures. Where the gases seep offshore, they form pockmarks and rise through the water column into the atmosphere. Gas migration and seepage implies that the onshore and offshore faults systems are permeable and that they were active recently and simultaneously. The latter can be explained by a transtensional system involving two right-stepping, right-lateral NW-SE trending faults, either binding a pull-apart basin between the islands of Malta and Gozo or associated with minor connecting antitethic structures. Such a configuration may be responsible for the generation or reactivation of faults onshore and offshore the Maltese Islands, and fits into the modern divergent strain-stress regime inferred from geodetic data.

Description: Published

Description: 361-374

Description: 6A. Geochimica per l'ambiente e geologia medica

Description: JCR Journal