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In this study we determined the stress regime acting along the East Anatolian Fault Zone between Turkoglu (Kahramanmaras) and Celikhan (Adiyaman), from the Neocene to present-day, based on the inversion of striations measured on faults and on the focal mechanisms of earthquakes having magnitudes greater than 5.0. The inversions yield a strike-slip stress regime with a reverse component (i.e., transpression) operative in the Neocene to present with a consistent N-to NW-trending σ 1 axis 156 ± 11• and an E-to NE-trending σ 3 axis, 67 ± 9• σ 3 , producing left-lateral motion along the East Anatolian Fault Zone. The inversions of focal mechanisms yield a strike-slip stress deviator characterized by an approximately N-S (N1• W)-trending σ 1 and an approximately E-W (N89• E)-trending σ 3 axis. Both the kinematic analysis and structural observations indicate that the stress regime operating in the study area has had a transpressional character, giving rise to the Mio-Pliocene compressive structures (reverse faults, thrusts and folds) observed in the study area. Field observations allow estimation of a Pliocene age for the strike-slip East Anatolian Fault Zone.

In the eastern Mediterranean, plate motions occur between the Arabia/Anatolia, Africa/Arabia and Anatolia/Africa boundaries along the Amanos Fault, the Dead Sea Fault and the Cyprus Arc, and the extension of the latter on land. Detailed enhancement and classification procedures applied to SPOT XS imagery of the Hatay region, and centred on the Quaternary Amik Basin, have revealed a prominent NE-SW-trending tectonic lineament. Recent seismicity suggests that this NE-SW-trending lineament dies out in the Quaternary Amik Basin in the east and continues to the Cyprus Arc to the south-west. Structural lineament extensions derived from SPOT XS imagery using linear edge enhancement and unsupervised classification methods and the distribution of seismicity in the Hatay region show that this region has been affected by the East Anatolian Fault Zone, the Dead Sea Fault Zone and the Cyprus-Antakya Transform fault. These fault associations accommodate northerly movement of the African and Arabian plates toward the Eurasian plate. The Amik Basin appears to have been formed by interaction among the Amanos Fault interpreted here as a continuation of the East Anatolian Fault the left-lateral Dead Sea Fault, and the left-lateral Cyprus-Antakya transform fault. Active faults belonging to the aforementioned structural zones meet one another to form a triple junction at the Amik Basin near Antakya.

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Fault kinematic analysis and inversion of focal mechanisms of shallow earthquakes reveal significant evolution of the regional stress regime in the northeastern most corner of the Eastern Mediterranean region since the Mio-Pliocene to the present time. This study was carried out in the interaction area between the Arabian/African plates and the Anatolian block. The evolution of stress regimes consists of a change from older transpression to younger transtension. Both strike-slip stress regimes having a NNW-to northwest-trending σ Hmax (σ 1 ) and ENE-to northeast-trending σ Hmin (σ 3 ) axes induce a sinistral component of displacement on the major intra-continental Karatas-Osmaniye and Misis-Ceyhan faults elongated with the northeast-trending Misis Range between Adana and Osmaniye provinces (sub-area i) and by a NNE-trending plate boundary Amanos fault running along Amanos Range between Antakya and Kahramanmaras provinces (sub-area ii). The inversion results show that the transtensional stress regime is dominantly strike-slip to extension, with an ENE-to northeast-trending σ Hmin (σ 3 ) axis for subareas (i) and (ii), respectively. The inversions of earthquake focal mechanisms indicate that the transtensional stress regime is still active in the whole study area since probably recent Quaternary time.