Date

2014-12-15

Author

Delph, Jonathan R.
Kahraman, Metin
Zandt, George
Beck, Susan L.
Özacar, Atilla Arda
Turkelli, Niyazi

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Western Anatolia is one of the most seismically active regions in the world, undergoing broad N-S extension associated with the rollback of the Aegean slab in the south. This region is characterized by high heat-flow, recent volcanism, and core-complex formation. We use >3500 receiver functions from a dense array of 47 stations located in western Turkey and dispersion data from a recent regional-scale, ambient noise tomography study to invert for shear-wave velocity as a function of depth. Using this technique, we obtain an unprecedented three-dimensional shear-wave velocity model that characterizes the crust of western Turkey. We find a sharp Moho transition beneath much of western Anatolia, with crustal thickness varying from ~25 km near the Aegean Sea to ~35 km beneath the Fethiye Lobe correlating with the topography in western Turkey. The lower crust exhibits a relatively continuous ~10-15 km thick low shear-wave velocity layer (LVL) beneath most of western Anatolia, reaching velocities below 3.0 km/s in some places. The top of this LVL marks the lower boundary of crustal seismicity. These characteristics suggest that the lower crust in western Anatolia is behaving as a ductile solid, as seismic velocities in this range at lower crustal depths are indicative of the presence of fluids (possibly partial melts when considering the high heat-flow in the region). We propose that the lower crust in this region may be undergoing local crustal flow due to the N-S dominated stress regime, which led to the formation of the sharp, low-relief Moho observed in western Turkey. Across the Fethiye-Burdur Fault Zone, we see the slowest S-wave velocities in the lower crust, reaching ~2.8 km/s. Unlike elsewhere in western Turkey, this region has relatively low surficial heat-flow and no recent volcanism. Therefore, the anomaly in the Fethiye Lobe is likely due to a different mechanism than western Turkey. We also observe a very slow uppermost mantle beneath this region, with shear-wave speeds < 4.2 km/s. We attribute this anomaly to subduction related processes, such as the introduction of aqueous fluids from the underthrusting of thick, hydrated sediments or alternatively, to possible serpentinization of the upper-mantle. Mantle wavespeeds transition to more typical velocities across the Fethiye-Burdur Fault Zone.

Subject Keywords

Continental tectonics: general, Dynamics of lithosphere and mantle: general

URI

https://abstractsearch.agu.org/meetings/2014/FM/T13A-4627.html
https://hdl.handle.net/11511/94880

Collections

Department of Geological Engineering, Conference / Seminar