Thesis defense of David DELLONG

Active rifts and deep structure of the Eastern Sicilian margin

The Ionian basin in the central Mediterranean is exposed to several destructive earthquakes, sometimes accompanied by tsunamis, which were recorded in the past (Catania in 1693, Messina in 1908). However, the identification of faults and the tectonic regime related to these events is still debated in the scientific community. Moreover, from a geodynamic point of view, the importance of this basin lies in the fact that it shelters a subduction undergoing a “withdrawal of the diving plate” towards the Southeast since the last 35 Ma. This phenomenon is designated as responsible for the movements of large continental Mediterranean blocks such as the Corso-Sardinians (Corsica and Sardinia) and Calabro-Péloritain (Sicily and southern Italy). Mechanisms related to these large movements (over 700 km) are not fully understood and are the subject of much scientific debate. My thesis aims to identify some major flaws and improve the understanding of this subduction system and the East-Sicilian margin.

The DIONYSUS campaign, which took place in October 2014 aboard the German ship R / V Meteor, was a project led by four European institutes: Ifremer and CNRS-UBO (in France), Geomar (Germany) and INGV Rome (Italy) . This campaign collected wide-angle seismic data with 153 deployments of OBS (for Ocean Bottom Seismometer or Sea-bottom Seismometers), multitrace seismic reflection and bathymetry, along five profiles in the basin (see map). This type of data will make it possible to study the deep structure of the Ionian basin and the eastern Sicilian margin (up to 30 km deep). Two theses are currently in progress and model the OBS data of three profiles at Geomar and two in France between Ifremer and CNRS-UBO.

The velocity models obtained by modeling the two profiles (named DYP1 and DYP3) make it possible to identify several major structures. First of all, the probable position of a great fault called STEP (for Transform Edge Propagator) which is a great lithospheric tear fault, and which is related to the withdrawal of the diving plate. These models also allow us to image the deep structure of the oceanic cost of the basin as well as the Maltese Escarpment which is interpreted as an old transforming margin. This results are important for understanding the geodynamics of the basin.

Keywords

Active rifts, earthquakes, Seismic Wide-angle, Mediterranean, Italy, Sicily, Calabria, Eastern-Sicilian Margin, Geodynamics, Deep Structure, Crustal

Thesis Director (s): Frauke Klingelhoefer (Ifremer) & M-A Gutscher (LGO)