Abstract:

On 6 February 2023, East Anatolia was devastated by two major earthquakes resulting in hundreds of thousands of collapses and tens of thousands of human casualties, and injured and homeless people. These high numbers are attributed to the extensive heavy and very heavy structural damage corresponding to damage grades 4 and 5 in terms of the European Macroseismic Scale EMS-98 that were caused in the earthquake-affected area.The obvious reasons that contributed to the disaster comprised the large magnitude of the earthquakes, the generation of the first earthquake during the night that found the majority of the population in their homes, the demographic characteristics of the region that include densely built-up and populated areas as well as the proximity of many residential areas to the ruptured faults. Furthermore, the synergy of significant factors, which are strongly related to the seismotectonic setting of the area, the earthquake environmental effects (EEEs) and the characteristics of the affected structures resulted in one of the largest earthquake disasters in the modern history of the country.The aim of this study is to highlight the factors related to building properties and the generation of EEEs that control the grade and the spatial distribution of building damage in the studied earthquake-affected areas of southeastern Turkey. The results of this study are based on field surveys conducted by the authors shortly after the earthquakes (7 to 11 February) and after almost 2 months (31 March to 6 April). The field survey comprising conventional methods of geological mapping and modern and innovative methodologies such as deployment of Unmanned Aerial Systems (UAS).In regards to the building construction properties, the loose enforcement of the building code, the random urban planning solutions and the poor construction standards are the main construction deficiencies that led to one of the largest disasters in Turkey’s recent history.Regarding geological factors, the triggering of primary and secondary EEEs largely shaped the grade and distribution of damage. Where coseismic surface ruptures intersected with the built environment, heavy to very heavy structural damage was observed. This was evident in many cases along the ruptured segments of the East Anatolian Fault Zone. Liquefaction observed close to waterbodies caused damage typical of building foundation load-bearing capacity loss. The earthquake-triggered landslides affected mainly mountainous and semi-mountainous settlements characterized with pre-earthquake high related susceptibility. The high susceptibility to generation of EEEs was extensively confirmed in many cases resulting in extensive damage.