Coseismic deformation and kinematic rupture process of the 2023 Türkiye <i>M</i>W7.8–7.5 earthquake doublet deduced from high-rate GNSS observations

SUMMARY On 2023 February 6, a devastating earthquake doublet struck in Türkiye, which caused tremendous damage including about 54 000 fatalities. We use high-rate global navigation satellite system (GNSS) data to study the coseismic static and kinematic displacement, and invert for fault slip distribution of the earthquake doublet. The maximum static coseismic displacements for the Mw7.8 (EQ1) and Mw7.5 earthquake (EQ2) are 0.38 and 4.4 m, respectively. The kinematic displacement recorded by GNSS stations reflect clearly the earthquake rupture process in more detail. We utilize 1-Hz GNSS waveforms, GNSS static displacements and surface rupture measurements to invert for the kinematic rupture model of the earthquake doublet. Our results show a rupture duration of ∼80 s, faulting length ∼350 km and maximum slip ∼7.4 m for EQ1, and a rupture duration of ∼35 s, rupture length ∼190 km and maximum slip ∼9.2 m for EQ2. The slip distributions inverted solely from GNSS coseismic deformation are basically consistent with the results from multisource data. The rupture velocity of EQ1 towards east is about 4.5 km s−1 towards the east and 3.2 km s−1 towards the west. EQ2 nucleates on Çardak fault with bilateral supershear rupture velocity of 5.0∼5.5 km s−1 within the first 0–12 s, subsequently transitioning to subshear rupture at a speed of 1.2 km s−1 towards the east and 3.0 km s−1 towards the west. Our finding of the bilateral supershear ruptures of EQ2 contrasts with the results of unilateral westward supershear rupture of previous studies. We think that this discrepancy could be attributed to the utilization of more geodetic data of the relatively denser GNSS stations in the east flank of EQ2’s epicentre and calculating the mean velocities for individual rupture intervals in this study.