Long-term Aftershock Properties of the Catastrophic 6 February 2023 Kahramanmaraş (Türkiye) Earthquake Sequence

Abstract Nine hours apart, two catastrophic earthquakes (Mw 7.8 and 7.6) occurred on 6 February 2023, in eastern Türkiye. The mainshocks destroyed several cities and villages in 11 provinces, including Kahramanmaraş, Hatay, Adıyaman, Malatya, Adana and Gaziantep. Over about 50,000 aftershocks were detected in the nine months. Because the resolution of hypocentral locations in the Turkish national earthquake catalogs is limited, about 31,000 events are relocated using the double-difference method in this study. The aftershock distribution and its relation to energy release on the faults and Coulomb stress change areas are investigated. The improved hypocenters give a clearer image to understand the activity on the faults. The event distribution indicates that the rupture of the first mainshock in Pazarcık (Mw 7.8) propagates unilaterally on the northernmost segment of the Dead Sea Fault Zone and then transfers to the East Anatolian Fault Zone at the Maraş Triple Junction. The bilaterally extending rupture causes dense aftershock activity on the fault zone from Samandağ to Pütürge. The second mainshock in Elbistan (Mw 7.6) was triggered because of the positive Coulomb stress change on the Çardak fault, which generates dense clusters at both ends of the fault. It is observed that a high number of aftershocks occur on the low slip patches, and the high-energy release areas have low activity because of the stress equilibrium on the fault surfaces.