Present-day strain accumulations and fault kinematics at the Hatay Triple Junction using new geodetic constraints

The East Anatolian Fault (EAF), Cyprus Arc and Dead Sea Fault (DSF) intersect at the Hatay Triple Junction (HTJ) in southern Turkey, which is a tectonically controversial zone among researchers. Although it is not as active as the North Anatolian Fault (NAF) or other segments on the EAF in terms of seismicity, the HTJ accumulates strain causing considerable seismic activity in the region. Prior to this study, the strain accumulations and kinematics of the HTJ have not been precisely investigated using such a dense GPS network comprising permanent GPS stations, Turkish National Fundamental GPS Network (TUTGA) and campaign sites. Here, the fault slip rates and locking depths were constrained in the vicinity of HTJ using a new velocity field and improved block modeling. As per the results of block modeling, the EAF and Karatas-Osmaniye Fault (KOF) are fully locked down to depths of 15 km and 7 km, respectively. Furthermore, the Karasu Fault (KF) has a fully locked seismogenic zone to 7 km depth with a similar slip distribution to the EAF. Our kinematic model suggests 9.2 mm/yr left-lateral strike-slip rate and 2.0–2.7 mm/yr thrust faulting slip rate at the southwest end of the EAF. The KF appears to have left-lateral strike-slip at the rates ranging 4.0–5.5 mm/yr, while contrarily it has no significant normal/reverse faulting component. In addition, the KOF accommodates left-lateral strike-slip of 3.3–4.5 mm/yr and extension with the rates of 1.8–2.7 mm/yr. The new constraints on the fault slip rates associated with the HTJ correspond to predictions for a probable large earthquake with possible magnitude ranging from 7.2 to 7.6 for the EAF segment and 6.7–7.2 for the KF and KOF segments.