On February 6, 2023, an M_w7.8 earthquake hit the south of Kahramanmaras prefecture, Turkey, followed by another M_w7.5 earthquake after nine hours in the middle region of the Kahramanmaras prefecture. More than 84,000 buildings collapsed or were severely damaged, and more than 50,000 lives were lost in Turkey and Syria. Some of the authors, as members of Chinese rescue team, entered Antakya, Hatay prefecture, and investigated the damaged buildings. This paper first summarizes the damage patterns of buildings and provides three reasons for the massive number of collapsed buildings; i.e., the lack of seismic measures for better ductility, site effects such as liquefaction and surface rupture, and pronounced low-frequency components of the ground motions. Next, the seismic responses of two typical buildings are calculated based on the geometric data estimated by visual inspection. The results imply that the resonance of the whole structure and the poorer ductility of key members resulted in the collapse of buildings. Finally, some conclusions are drawn. Note that although a large number of buildings were seriously damaged to collapse, the majority of buildings in the areas of extreme shaking were lightly or moderately damaged, which implies that well designed and constructed buildings were able to survive and protect human lives even in over-design earthquakes.