Determination of recent tectonic deformations in the vicinity of Adana-Osmaniye-Hatay-Gaziantep triple junction region by half-space modeling

Abstract

Recent earthquakes on the East Anatolian Fault Zone (EAFZ) and its surroundings in the Eastern Mediterranean region reveal a potential seismic hazard. It is thus needed to constrain deformations within tectonically active zones and clarify kinematics of the triple junction near Adana, Osmaniye, Hatay, and Gaziantep provinces. To understand strain accumulations and interseismic patterns of these active zones, one of the most popular geodetic methods was applied. Slip rates derived from Global Positioning System (GPS) observations by half-space modeling lead us to predict possible magnitudes and even probable locations of future destructive earthquakes. In this context, we form a region-specific GPS network consisting of both campaign observation sites and permanent stations to monitor strain accumulations across major active faults and investigate fault kinematics in detail. The campaign GPS data sets acquired in 2009, 2010, 2011, and 2019 were merged with data from different local permanent GPS networks for an integrated analysis of the determination of recent tectonic deformations. The TDEFNODE software was used to construct a kinematic model in an elastic and homogeneous half-space. The modeling approach needs inputs such as block and fault geometries, GPS site velocities, and locking depth assumptions. Our kinematic model indicates that an almost purely sinistral strike-slip rate of 7.5 mm/yr without any significant normal or reverse component is dominant on the main branch of the EAFZ. This estimated slip rate supports a prediction for a magnitude margin of 7.2-7.6 for the next probable large earthquake on the Turkoglu-Golbasi segment. The Karatas-Osmaniye Fault has a 3.4 mm/yr dextral strike-slip rate together with a reverse-slip rate of 3.1 mm/yr, which corresponds to a possible magnitude of 6.8-7.1 for an earthquake on the southwest end of the East Anatolian Fault. The Karasu Fault extends from the Turkoglu Triple Junction on the EAFZ in the north to the Hatay Triple Junction in the south. This critical fault segment has a sinistral 4.4-5.4 mm/yr slip rate with a normal component slip rate of 3.0 mm/yr, supporting earthquake prediction with a possible magnitude of 6.8-7.2. As a result, the determination of such kinematic indications in active tectonic zones by GPS observations plays a key role in seismic hazard analysis for the Eastern Mediterranean region.