6 February 2023 Kahramanmaraş Earthquake Sequence: ‘supercycle’ events within a complex tectonic setting

On 6 February 2023, a series of earthquakes struck south-eastern Türkiye and northern Syria, causing a death toll of more than 50.000 people and an economic loss of billions of US Dollars. The devastating sequence started with the Mw ~7.0 Narlı Earthquake along a subsidiary splay, which was then instantly followed by the Mw 7.8 Pazarcık Earthquake bilaterally rupturing multiple structural elements in a complex triple junction system. These were followed ~9 hours later by the Mw 7.6 Elbistan Earthquake that took place on the Çardak and the Yeşilyurt faults. The involvement of multiple faults and the immense size of the affected region raise multiple questions such as the controlling factors, especially on the extent of the rupture length, slip distribution, width of the rupture zone, and any potential seismic gaps that were brought closer to failure.

This study aims to present our field investigations and measurement for the 6 February 2023 earthquakes with a particular emphasis on the tectonic complexity of the region. We have constructed a detailed surface rupture map and documented hundreds of offset measurements that suggest up to ~7 and ~8.5 meters of maximum sinistral displacements, for the Pazarcık and Elbistan earthquakes, respectively. The co-seismic slips differ from the offsets of the penultimate event in places, suggesting a variable slip behaviour, especially for the Çardak Fault. Our map does not only include the Principal Displacement Shear (PDS), but also almost all the secondary shears that provide an opportunity to determine the deformation width along the faults. One of the widest zones of surface breaks is observed within the Palaeozoic metamorphics and Mesozoic limestones of the Nurhak Mountain along the Çardak rupture, highlighting the influence of structural complexities on the distribution of deformation. A similar control occurs at the northeastern tip of the Pazarcık Rupture, which terminates in another structural complexity where the left-lateral East Anatolian Fault (EAF) connects with the Bitlis-Zagros suture zone. Field data suggests that this structural junction is responsible for arresting the rupture along the EAF, not the southern termination of the 24 January 2020 Mw 6.8 Sivrice (Elazığ) Earthquake rupture, producing a ‘seismic gap’ of about 20 km. To the south, the Pazarcık rupture reached the Dead Sea Fault, which has not had a significant surface rupturing earthquake to the north of Aqaba since the early 11th century.  Despite the widespread destruction that razed several towns to the ground, the 2023 Kahramanmaraş Earthquake Sequence provides invaluable information on understanding the geometry and kinematics of active faulting that accommodate the Eurasia-Africa-Arabia convergence in the eastern Mediterranean.