The seismic cycle of the Hatay Triple Junction from GNSS analysis: interseismic, coseismic and postseismic deformations

Abstract

The East Anatolian Fault Zone (EAFZ) is a major tectonic feature in Anatolia, moving westward relative to the Eurasian plate, primarily due to the compressional behavior of the African, Sinai, and Arabian plates. The EAFZ has been historically significant as the epicenter of several major seismic events, including the recent devastating earthquakes in Kahramanmaraş on February 06, 2023. In this study, we provide a comprehensive tectonic analysis of the EAFZ, focusing specifically on the Hatay Triple Junction (HTJ), where the EAFZ meets with the continuation of the Dead Sea Fault Zone and the Cyprus Arc. Through the synthesis of pre-seismic evaluations and co-seismic data derived from our comprehensive geodetic network, we aim to extend the understanding of the seismic cycle and fault behavior in this tectonically complex region. In the pre-seismic phase, we employed a dense GNSS network, including the Turkish National Fundamental GPS Network (TUTGA) and various campaign sites, to analyze the strain accumulation and fault kinematics at the HTJ. Analyses revealed that the EAFZ and Karataş-Osmaniye fault exhibit complete locking at depths of 15 km and 7 km, respectively, while the Karasu Fault (KF) demonstrates locking up to a depth of 7 km. Our kinematic models indicated significant slip rates, suggesting a high potential for large earthquakes. Remarkably, during the revision of our manuscript in “Tectonophysics”, two major earthquakes (Mw 7.7 and Mw 7.6) occurred near the KF and EAFZ in Pazarcık and Elbistan, Kahramanmaraş, respectively. These earthquakes, happening in close succession, dramatically corroborated our predictions for seismic activity near the HTJ.  In the co-seismic phase, following the Kahramanmaraş earthquakes, we utilized a high-resolution GNSS network with 73 permanent and 40 campaign stations to assess surface displacements and fault slip distributions. Significant displacements were recorded, with the largest being 466 cm, and substantial fault ruptures were observed along the EAFZ and Çardak fault segment, including the left-lateral slips of 494 cm and 391 cm in the first and second earthquakes, respectively.   Our ongoing projects will integrate pre-earthquakes geodetic data with new GNSS measurements to analyze the postseismic deformation following the Kahramanmaraş earthquakes, including afterslip and its relation with aftershocks, as well as stress perturbations on the neighboring faults. This integrated approach is expected to further refine our ability to understand the behavior of the fault in the post-seismic phase and delineate the complete seismic cycle along the EAFZ.