Date

2013-12-09

Author

Biryol, C. Berk
Beck, Susan L.
Zandt, George
Özacar, Atilla Arda

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The tectonics of the Mediterranean region is characterized by an intricate configuration of arcuate subduction zones and mountain belts. The evolution and the geodynamics of these zones are controlled by closure of Tethys Ocean and the convergence of the Eurasian and the African plates. The interplay between convergence-related compression and slab rollback related extension throughout the convergence zone is further complicated by processes such as termination of subduction, and tearing and detachment of subducting oceanic lithosphere. Our recent studies using shear-wave splitting and finite-frequency P-wave teleseismic tomography reveal the complexity of upper mantle structures and associated mantle flow patterns in the eastern Mediterranean, beneath the Anatolian plate. In our studies we use data from over 200 seismic stations belonging to several temporary and permanent seismic networks. Our tomography results reveal segmented fast seismic anomalies beneath Anatolia, which we identify as the Aegean and the Cyprus slabs that are separated from each other by a tear as wide as 300 km beneath Western Anatolia. The geometry of this tear suggests it was formed by differential subduction and rollback rates along the Aegean and Cyprus trenches and hence down dip, upper mantle continuation of a Subduction Transform Edge Propagator (STEP) fault. This configuration of slabs and the associated geodynamic setting is consistent with our upper mantle seismic anisotropy observations from shear-wave splitting measurements. The fast polarization directions inferred from the shear-wave splitting favors a SW direction of asthenospheric flow. We infer that this flow is controlled by the differential forces acting on the upper-mantle exerted by the slab-roll-back taking place along the Aegean and the Cyprean Subduction Zones. The gap associated with the tear between Aegean and the Cyprus slabs is occupied by slow velocity material that we interpret as hot upwelling asthenosphere. The eastern termination of the subducting African lithosphere is located near the transition from central Anatolia to the Eastern Anatolian Plateau or Arabian-Eurasian collision front that is underlain by large volumes of hot asthenosphere marked by slow velocity anomalies. The slow velocity anomalies that occupy the gaps and tears both in the east and in the west underlie major volcanic provinces of Anatolia. Overall, our observations hold important clues about the evolution and the geodynamics of the eastern Mediterranean subduction zones as well as tectonics of the overriding Anatolian Plate and its surroundings. Incorporation of observations from our recent seismic deployment in the central Anatolia (Continental Dynamics - Central Anatolian Tectonics Project) will provide further constraints on shallower sub-crustal structure in the region.

URI

http://abstractsearch.agu.org/meetings/2013/FM/sections/T/sessions/T24B/abstracts/T24B-03.html
https://hdl.handle.net/11511/94839

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Department of Geological Engineering, Conference / Seminar