We use survey and continuous GPS observations during the period 1997–2010 to investigate active deformation in the Isparta Angle region of SW Anatolia, Turkey. This region, bordered by the Fethiye Burdur Fault Zone (FBFZ) in the west and the SE extension of the Aksehir Simav Fault Zone (AKSFZ) in the east, accommodates a part of the active deformation of W Turkey. Our results show that the Isparta Angle region rotates counter-clockwise (CCW) with respect to Anatolia. Both the FBFZ and the AKSFZ are predominantly transtensional boundaries that accommodate southward motion of the Isparta region with respect to Anatolia. The FBFZ has left-lateral strike-slip behaviour along its SW segment that changes to right-lateral strike-slip along its NE extension. This change in the sense of strike-slip motion is accommodated by extension on a NW–SE striking normal fault system that is associated with the Menderes Graben system. Transtensional fault systems along the boundaries of the Isparta Angle with Anatolia are inconsistent with extrusion models for present-day southward motion. An increase in motion rates towards the Hellenic and Cyprus arc subduction systems, and CCW of the Isparta region, supports dynamic models involving active rollback of the subducting African Plate, toroidal mantle flow around the eastern edge of the subducting African slab near the Hellenic arc/Florence Rise junction, and/or gravitational collapse of the overriding Anatolia Plate.

Southwestern Turkey is a tectonically active area. To determine kinematics and strain distribution in this region, a GPS network of sixteen stations was established. We have used GPS velocity field data for southwest Anatolia from continuous measurements covering the period 2003 to 2006 to estimate current crustal deformation of this tectonically active region. GPS data were processed using GAMIT/GLOBK software and velocity and strain rate fields were estimated in the study area. The measurements showed velocities of 15-30 mm/yr toward the southwest and strain values up to 0.28-8.23x10^-8. Results showed that extension has been determined in the Burdur-Isparta region. In this study, all of strain data reveal an extensional neotectonic regime through the northeast edge of the Isparta Angle despite the previously reported compressional neotectonic regime. Meanwhile, results showed some small differences relatively with the 2006 model of Reilinger et al. As a result, active tectonic movements, in agreement with earthquake fault plane solutions showed important activity.

On 19 May 2011, an earthquake of magnitude Mw:5.9 occurred just 9.1 km below the surface of the earth on the Simav fault in Turkey. The region is located north-west of the Gediz graben, one of the major tectonic structures in the extensional regime of western Anatolia. In this study, from 2009 to 2011, the data from nine Continuously Operating Reference Stations (CORS-TR) in the region and one permanent Global Navigation Satellite System station working locally were assessed and analysed using GAMIT/GLOBK software. The behaviour of these stations before and after the earthquake was analysed using calculated time series. At the same time, the strain and rotation rates of current deformation in the Simav region were computed using the 2008–2011 data from the CORS-TR network. The directions obtained from the focal mechanism solutions and strain analysis of the Simav earthquake were observed as being in harmony. Nonetheless, Simav earthquake caused a displacement of 1–2 mm (approximately) in nearby locations. The Simav earthquake shows that the extensional regime in western Anatolia has recently been active in the region and is a good example of the evolution of the graben system.

Comparison of Palaeostress Analysis, Geodetic Strain Rates and Seismic Data in the the Western Part of the Sultandağı Fault in Turkey