Study of valley effects in Göksun District (Türkiye) during the 6th February earthquakes

Two successive devastating earthquakes occurred in Eastern Türkiye on the 6th of February 2023. The epicenter of the Pazarcik earthquake was 45 km west of the city of Gaziantep, with a depth and moment magnitude of the event are 8.6 km and 7.7, respectively. A second event (Elbistan) occurred 66 km northeast of Kahramanmaras just nine hours after the first. The second event’s depth was 7 km, and its moment magnitude was 7.6. The characteristics of ground motion distribution during these events were unusual. The epicenter of the first event triggered the Eastern Anatolian fault system, producing surface shear ruptures surpassing 300 km. On the other hand, the Elbistan earthquake showed a more expected behavior, with seismic movements presenting an attenuating behavior. Göksun city and the periphery were an exception here, while the city is embedded in a valley, and the distance between the city and the epicenters of the first and second events were 68.66 km and 95.6 km, respectively. The maximum acceleration recorded at the 4612 station was about 0.815 g and 0.144 g for the Elbistan and Pazarcik earthquakes, respectively. In this paper, in-depth analyses were carried out to study the valley effects produced during the 6th of February earthquakes in Göksun. The results of analyses clearly prove the role of the site effects during these events. These site effects, accompanied with the very low quality of the building stock, were the reasons for widespread destruction and damage.