Two simultaneous earthquakes occurred in the Kahramanmaraş-Pazarcık and Kahramanmaraş-Elbistan districts of Turkey on February 6, 2023, and with magnitudes of 7.7 and 7.6, respectively. These events caused the highest estimated loss recorded in Turkey within the last century from natural disasters. The key reason for the extensive loss was the proximity of eleven cities to the earthquake epicenters. Middle East Technical University teams investigated the building sites in Gaziantep, Kahramanmaras, Hatay, Adiyaman and Adana. The ground motion recordings revealed that in certain locations of Gaziantep, Kahramanmaraş and Hatay, the ground motion levels exceeded the maximum credible earthquake level defined for a return period of 2,475 years in the Turkish Earthquake Code. Residential building performance was investigated with respect to the construction year, which is a good indicator of compliance with modern seismic codes and inspection procedures. About 97% of the collapsed buildings were constructed prior to 2000, whereas over 5,000 buildings, which were built after 2000, collapsed or required urgent demolition. Most of the buildings with minor or greater structural damage sustained heavy infill wall damage rendering occupancy impossible. Aside from damage in older construction with significant structural deficiencies, the damage in some of the more recent and better constructed buildings was observed to be surprisingly poor. This can be attributed to the level of ground motion, significant ductility demands, poor material and workmanship and damage to non-structural elements. With the estimated total loss of above 100 billion dollars and over 50,000 casualties, the current seismic design criterion based on ductility and acceptance of structural damage should be re-evaluated to ensure a more resilient urban environment in high seismic regions.