21 novembre 2006 ( dernière mise à jour : 1er juin 2017 )
Durée : 2006 - 2011
Coordinateur : Anne Paul (ISTerre)
Equipe ISTerre impliquée :
Ondes et structures
Collaborations extérieures :
Université Bogazici (Istanbul),
Université Aristote (Thessalonique).
Résumé en anglais :
SIMBAAD -Seismic Imaging of the Mantle Beneath the Aegean-Anatolia domain
The Aegean-Anatolia region is the most strongly deforming zone of the Euro-Mediterranean area. Although the part played by the retreat of the Hellenic trench in the Aegean extension is rather well understood, the driving mechanism of the westward motion of Anatolia is debated . A better understanding of the relations between surface deformation and mantle flow requires high resolution data on mantle structure and anisotropy. This was the goal of the SIMBAAD project (ANR-06-BLAN-0317) which relied on the installation of 80 temporary broadband seismic stations complementing for 2 years (2007-2009) the 150 stations of the permanent broadband networks of Turkey and Greece.
We have shown that : 1) The overall mantle structure beneath the Aegean Sea and Anatolia is characterized by a low-velocity zone (80-200 km depth) reflecting a slow and warm asthenosphere underlying a thin lithosphere . Beneath Anatolia, at depths larger than 200 km, our shear-wave tomography delineates high-velocity bodies which might betraces of subducted slabs. The westernmost anomaly is separated from the Hellenic slab by a low velocity anomaly which we interpret as a vertical slab tear beneath southwest Anatolia (PhD thesis G. Salaün, Salaün et al., GJI 2012). 2) In Western Anatolia (28°E), we image small-amplitude and long-wavelength undulations of the Moho topography, suggesting that widespread extension and viscous flow in a hot lower crust have smoothed out the lateral variations of crustal thickness induced by Cenozoic continent-continent collision (Karabulut et al., GJI, in revision) ; 3) Fast-velocity directions in the mantle measured from the splitting of SKS phases display very stable NE-SW orientations from the Aegean to eastern Anatolia which could all be due to trench-normal flow induced by the retreat of the Hellenic slab. They however are oriented at an angle from the westward displacement of Anatolia, suggesting that the extrusion of Anatolia either has not yet imprinted the mantle anisotropy, or that there is no E-W mantle flow and basal drag beneath Anatolia (Paul et al., in prep.).
Dans la même rubrique :