Coseismic and Postseismic Deformations of the 2023 Turkey Earthquake Doublet

On 6 February 2023, an earthquake doublet of Mw 7.8 and Mw 7.5 occurred in southeastern Turkey and caused surface ruptures over 350 km for the eastern Anatolian fault (EAF) and 150 km for the Surgu fault (SF), respectively. Over 3700 Mw > 3.0 aftershocks occurred within 5 months following the earthquake doublet, indicating that postseismic stress adjustment is evident. Here, we utilize InSAR technology to investigate the earthquake doublet in terms of its coseismic and postseismic deformations and to estimate the changes in Coulomb stress. We found that the postseismic surface deformation is consistent with the coseismic rupture, characterized by left-lateral strike-slip movement. The coseismic deformations (>5 m) are concentrated in the central-eastern (Pazarcik and Erkenek) segments in the EAF and the central (Cardak) segment in the SF. Notably, the maximum coseismic slip (up to 10 m) and the largest postseismic slip (∼0.5 m) both occurred on the Cardak segment. Postseismic deformations (>0.05 m) are concentrated in the northeastern Erkenek segment and southwestern Amanos segment of the EAF, as well as the eastern Dogansehir segment of the SF. Compared with the coseismic deformation, the postseismic slip compensated for the insufficient deeper slip of the southwestern Amanos segment of the EAF and the central Cardak segment of the SF. Additionally, the postseismic slip extended the rupture area to both the northeast of the Dogansehir segment along the SF and the epicentral area of the 2020 Mw 6.7 earthquake along the EAF. The postseismic afterslip largely reduced the potential seismic hazard of the seismic gap between the eastern end of the coseismic rupture of the 2023 Mw 7.8 earthquake and the epicentral area of the 2020 Mw 6.7 earthquake, as well as the southwestern Amanos segment of the EAF and the eastern Dogansehir segment of the SF.