Tectonic and seismic activity of deep structures imaged by wide-angle seismic forward modeling in the Ionian basin (Central Mediterranean Sea).
Abstract
The Calabrian subduction zone is one of the narrowest arcs on Earth and a key area to understand the geodynamic evolution of the Mediterranean. Here in the Ionian Sea, the African plate subducts beneath Eurasia. Since roughly 35 Ma the subduction zone has been rolling back towards the SE, associated with a major lateral slab tear fault along its south-western side. This study presents data from a 350 km long wide-angle seismic profile spanning the complete suduction zone, gravity modelling and analysis of earthquake hypocenters. 61 marine seismometers from Ifremer and Geomar were deployed along the wide-angle seismic profile from the Dionysus (2014) cruise and located along the existing CROP-M2B deep seismic profile. The profile was extended on-land in NE Sicily using 6 stations from the INGV and spans the deep Ionian Basin and the accretionary wedge. The wide-angle seismic data were modeled using a forward approach and confirmed by gravity modeling. The subducting crust is about 5 km thick with velocities ranging from 6.5 km at the top to 7.25 km at the base and interpreted to be of oceanic in nature. The overlying 200-300 km wide accretionary wedge is up to 12 km thick and can be sub-divided into a pre- and a post-Messinian wedge. While the pre-Messinian wedge does not include evaporites, the post-Messinian wedge includes a 2-3 km thick layer of evaporites. The seismic velocities of the 5 sedimentary layers range from 2.0 to 4.5 km/s. The Calabrian-Peloritan block forming the backstop is up to 30 km thick and characterized by velocities and velocity gradients typical for continental crust. Together with the two companion wide-angle seismic lines crossing the E Sicily margin orthogonally and intersecting this long profile, we now have a regional data set which reveals the deep 3-D crustal structure and help us to reconstruct the geodynamic evolution of Southern Italy. Regional 3-D gravity modeling was performed using the software IGMAS in order to test two end-member hypotheses regarding the depth of the slab beneath the Calabrian-Peloritan block ; sandwiched together with the backstop crust or located roughly 10km deeper with a layer of intervening fore-arc mantle. Our work currently favors the former hypothesis. The hypocenter cross-sections indicate moderate seismicity within the crust and upper mantle of the downgoing slab.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T11H0246K
- Keywords:
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- 8102 Continental contractional orogenic belts and inversion tectonics;
- TECTONOPHYSICSDE: 8120 Dynamics of lithosphere and mantle: general;
- TECTONOPHYSICSDE: 8170 Subduction zone processes;
- TECTONOPHYSICS