Journal of Geodynamics 67 (2013) 78–96 Contents lists available at SciVerse ScienceDirect Journal of Geodynamics jo u r n al hom epage : http://www.elsevier.com/locate/jog Deformation of Central Anatolia: GPS implications  Bahadır Aktu˘ g a,∗ , Erdem Parmaksız b , Mustafa Kurt b , Onur Lenk b , Ali Kılıc ¸ o˘ glu b , M. Ali Gürdal b , Soner Özdemir b a Bogazici University, Kandilli Observatory and Earthquake Research Institute, Geodesy Department, Cengelkoy, Istanbul, Turkey b Geodesy Department, General Command of Mapping, TR-06100, Ankara, Turkey a r t i c l e i n f o Article history: Received 15 May 2011 Received in revised form 17 April 2012 Accepted 8 May 2012 Available online 19 May 2012 Keywords: Global Positioning System Crustal deformation Tectonics Plate tectonics Geodesy Geodynamics a b s t r a c t Central Anatolia plays a key role to connect the theories about the subduction of African Plate along Hellenic and Cyprian Arcs and the collision of Arabia indenter along Bitlis-Zagros Thrust Zone. Taking place between the North Anatolian and East Anatolian mega shear zones, the neotectonics of seismically less active Central Anatolia is often regarded as tectonic escape or extrusion tectonics. Although, avail- able GPS studies dating back to early 1990s reported coherent rotation, they were mostly focused on the seismically more active and more populated Western Anatolia and lack sufficient spatial resolution in quantifying second-order structures such as Tuz Gölü Fault Zone, Central Anatolia Fault Zone which comprises Ecemis ¸ Fault and Erciyes Fault, Ezinepazarı Fault and their related basins and associated pro- cesses. Besides, the new dense GPS velocity field of Central Anatolia exhibits systematic local patterns of internal deformation which is inconsistent with either coherent rotation or translation. The velocity gradients computed along the rotation profiles of Central Anatolia show nearly westward and smooth increments which cannot be explained through a simple rotation/transport of Central Anatolia Basin. Moreover, estimating and removing an Euler rigid-body rotation rate which is computed from the sites lying in the middle part of Central Anatolia absorbs the velocity discrepancies between the Eastern and Western part of Central Anatolia down to a few millimetres and leaves out systematic residuals. Upon completion of Turkish National Fundamental GPS Network (TNFGN) in 1999, early revision surveys were carried out in Marmara region because of the 1999 Marmara earthquakes. Additional observations were carried out in Central Anatolia, resulting in a velocity field of unprecedented spatial density with average inter-station distance of 30–50 km.We computed the horizontal velocity field with respect to a not-net rotation frame, to Eurasia, and to a computed Anatolia Euler Pole. Two distinct models of Anatolia neo- tectonics, microplate and continuum deformation were tested through the rigid-body Euler rotations, block modelling and strain analysis. The results show that the decomposition of the Eurasia-fixed veloc- ity field into the rigid rotations and the residuals reveals systematic residuals up to 5 mm/yr with respect to a computed best-fit Euler Pole located at 31.6820N ± 0.05, 31.6130E ± 0.02 and with a rotation rate of 1.3800/Myr ± 0.01. The relative velocities computed along rotation paths exhibit westward increasing linear gradients of 0.7–1.3 mm per 100 km depending on the latitude which is mechanically inconsistent with the assumptions of a coherent transport or a rigid rotation due to an extrusion in the east. Moreover, the strain analysis results show E-W extension rates up to 100 nanostrain/yr along approximately N-S striking faults within the region from the west of Karliova to Isparta Angle, which is another indication of the partitioned extensional strain across the Central Anatolia. On the other hand, the compressional strains were also obtained near the eastern branch of Isparta Angle, Tuz Gölü and southern Anatolia. In this study, we provide new quantitative results about the fact that the deformation in Central Anatolia is not uniform and possibly driven by the extension through slab pull and/or suction in west-southwest and the compression in the south rather than a simple coherent rotation and/or translation/transport of Anatolia driven by an extrusion process in the east. We also propose that the tectonics of Central Anatolia comprises a dominant tensional driving force along Hellenic Arc in the southwest and a restraining belt along Cyprian Arc in the south. © 2012 Elsevier Ltd. All rights reserved.  The manuscript solely reflects the personal views of the author and does not necessarily represent the views, positions, strategies or opinions of Turkish Armed Forces. ∗ Corresponding author. E-mail address: bahadir.aktug@boun.edu.tr (B. Aktu˘ g). 0264-3707/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jog.2012.05.008