Coseismic surface ruptures of M_W7.8 and M_W7.5 earthquakes occurred on February 6, 2023, and seismic hazard assessment of the East Anatolian Fault Zone, Southeastern Türkiye

On February 6, 2023, southeastern Türkiye experienced a devastating earthquake doublet along the East Anatolian Fault (EAF), with moment magnitude (M_W) values of 7.8 and 7.5. These strong earthquakes resulted in at least 50,000 deaths and severe economic losses. Systematic research on coseismic surface ruptures induced by these events is vital for assessing the cascade rupture behaviors of plate boundary faults and future seismic hazards in the region. Interpretation of high-resolution post-earthquake satellite images and field investigations yielded the following results: (1) the two strong earthquakes had separate rupture zones. The first earthquake generated an approximately 280 km coseismic surface rupture along the south-western segment of the main EAF, with 241 left-lateral displacements reaching up to 6.8±0.68 m, particularly 40 km northeast of the epicenter. The second earthquake produced a roughly 110 km surface rupture on an east-west branch of the EAF, with maximum displacements of 7.2±0.72 m. (2) The M_W7.8 earthquake resulted in a cascading rupture across multiple segments of the southwestern section of the main EAF, with significantly variable displacements. The northeastern and southwestern parts of the main EAF and Malatya Fault remain at risk of strong earthquakes in the future. (3) The EAF rupture zone is densely populated, and due to the site amplification effect of loose sediments on foreland alluvial fans, foundation failures of buildings in the populated areas are common. Therefore, it is crucial to enhance the future seismic fortification capabilities in urban and rural areas along the EAF.