Tectonic implications of the February 2023 Earthquakes (Mw7.7, 7.6 and 6.3) in south-eastern Türkiye

Abstract

The series of earthquakes that took place on February 6, 2023 caused one of the saddest major calamities in Türkiye. The first major earthquake of magnitude Mw7.7 broke the Pazarcık and Erkenek segments moving north on the East Anatolian Fault Zone (EAFZ) between Türkoğlu and Çelikhan. According to the Coulomb failure criterion, the Pazarcık earthquake (Mw7.7) increased stress on the Sürgü-Çardak Fault, a segment on the north splay of the EAFZ, and nine hours later the Elbistan earthquake (Mw7.6) occurred. This great event ruptured the Çardak Fault, the western part of the E-W trending Sürgü-Çardak Fault between Nurhak and Göksun. The Amanos Fault, which extends from Türkoğlu south to Antakya, broke almost simultaneously to the first Pazarcık earthquake. Similarly, the earthquake that broke the Amanos Fault transferred increased stress to its south-western neighbour, the Cyprus-Antakya Transform Fault, triggering the 6.3 magnitude Samandağ earthquake 14 days later. The February 2023 earthquakes, which caused the collapse of >100,000 buildings and the death of >50,000 people, created surface ruptures hundreds of kilometres in length and caused different displacements on different faults, the two largest of which were 4.6 and 6.7 m. On all the faults where the deadly earthquakes occurred in February 2023, inversion of the focal mechanisms of the earthquakes (main shocks and their aftershocks) indicates a transtensional stress regime, or a change from strike-slip to normal slip. For all strike-slip inversions, the R values are <0.45 indicating transtension. The stress tensors obtained indicate left-lateral movement with normal component on all faults where the earthquakes occurred. The transtensional regime, which is thought to reflect regional tectonics, is the result of forces caused by relative movements of Arabia, eastern Mediterranean and Eurasia.