The Destructive Earthquake Doublet of 6 February 2023 in South-Central Türkiye and Northwestern Syria: Initial Observations and Analyses

On 6 February 2023, two large earthquakes with magnitude 7.8 and 7.6 rocked south-central Türkiye and northwestern Syria. At the time of writing, the death toll exceeded 50,000 in Türkiye and 7200 in Syria. The epicenter of the first mainshock was located ∼15 km east of the east Anatolian fault (EAF), the second large earthquake (9 hr later) initiated ∼90 km to the north on the east–west-trending Sürgü fault. Aftershocks delin-eate fault lengths of ∼350 and ∼170 km, respectively. Using satellite and seismic data for first-order analyses of surface-fault offsets, space–time rupture evolution, and recorded ground motions, our study sheds light on the reasons for the extensive destruction. The first event ruptured the EAF bilaterally, lasted for ∼80 s, and created surface fault offsets of over 6 m. The second event also ruptured bilaterally with a duration of ∼35 s and more than 7 m surface offsets. Horizontal ground accelerations reached locally up to 2g in the first mainshock; severe and widespread shaking occurred in the Hatay-Antakia area with values near 0.5g. Both earthquakes are characterized by directivity effects and abrupt rupture cessation generating stopping phases that contributed to strong seismic radiation. Shaking was further aggravated locally by site-amplification effects.