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Zawartość zarchiwizowana w dniu 2024-05-27

submarine landSLIDEs and TSUnami MOdeling on the margins of the Mediterranean Sea

Final Report Summary - TSUMOSLIDE (submarine landSLIDEs and TSUnami MOdeling on the margins of the Mediterranean Sea)

Marine geohazards are usually caused by short-term geological events that affect offshore infrastructure or indirectly threaten coastal human communities, often areas of dense population that may double during tourist peak seasons. Submarine landslides occur mainly on ocean margins. Many submarine landslides are triggered by earthquakes, but the list of factors is quite broad including high sedimentation rates and geodynamic setting. Tsunamis are generated by sudden displacement of the seafloor due to earthquakes, submarine landslides or lateral collapse of volcanic ocean islands amongst most common causes.
TSUMOSLIDE (submarine landSLIDEs and TSUnami MOdeling on the margins of the Mediterranean Sea) will use (1) Geophysical and sampling tools to identify areas that have undergone recurrent failure and that could fail again, (2) numerical modeling in order to translate the geometry and sudden movement of submarine landslides into radial waves, (3) study the behavior of the wave when approaching the coastal zone and (4) identify areas of high risk to consider in regional standard geohazard plans.
Work started with bibliographic research in order to find the adequate modelling procedure for landslide and tsunami wave generation. Scientific literature allowed the fellow to identify the landslides that occurred in the Mediterranean Sea. A ground work was done by integrating all the identified landslide in a GIS software. Their characteristics, such as age of failure, dimensions before and after failure, sediment composition, have been introduced in tables.
The analysis of the rheological and failure behaviour characteristics of an identified landslide started using a numerical model developed by Imran et al., 2001. The output of the model are used as input data for the simulation of possible induced tsunami waves. One kick-off landslide has been selected. The inner and surface structure of the identified submarine landslide are studied by means of high-resolution 2-D seismic data combined with high-resolution multibeam bathymetry. The landslide occurred recently on the geological scale. It is situated in front of the Syrian Margin. As sediment cores are absent in this area, there is no direct information available on the sediment composition. Modelling by injecting crucial parameters in the model allowed to estimate the sediment composition by comparing the output of the model and the actual state of the landslide.
Significant results: Submarine landslides are ubiquitous along the continental margins of the Mediterranean basin and occur on tectonically-dominated margins as well as on passive margins and volcanic island flanks. Tectonically quiet zones seem to have the highest density of known events. Most landslides occur as long run-out distance debris flows, but slumps and deep-seated failures are also relatively common. In abyssal plains the distal product of massive failures is recorded as large megaturbidites, while on volcanic islands the dominant failure type is flank-collapse with development of debris avalanches. Submarine landslides, excluding megaturbidites, appear to occur in all water depths between the coastline and about 2000 m. Most landslides occupy areas ranging from a few to about 600 km2 and volumes up to 220 km3. The landslides headwall height are clustered around two modes: 0 to 40 m for relatively small landslides and 160 to 200 m for the largest ones. Most recorded submarine landslides are relatively young in age and several events appear to group near the Pleistocene to Holocene transition.