In 43 years of studying disasters I have seen few events that so clearly illustrate the primacy of vulnerability over hazard impact as does the Turkish-Syrian earthquake sequence of February 2023. Work at universities in Florida and Colorado strongly suggests that corruption is the principal cause of earthquake disaster, world-wide. The Turkish anti-seismic building codes have been revised five times in the last 55 years, including a thorough and intelligent upgrade in 2018. However, in 2016 and subsequently, there were amnesties that decriminalised those in the construction industry who ignored the laws, and those who modified buildings in ways that stopped them from being compliant with the regulations. Such practices were extremely widespread, the norm rather than the exception. This is also my experience from having spent extended periods in such buildings in Anatolia.
Videos and photographs of some of the 5,500 buildings that have collapsed tend to show that commonly there was total loss of structural integrity. While awaiting field missions to establish exactly why this happened, there is plenty of published research by Turkish seismic engineers to catalogue the common and widely repeated errors and omissions in Turkish reinforced concrete construction (see Google Scholar for citations). In synthesis, these are:
lack of shear resistance (i.e., quality) of the concrete
absence or lack of connectivity of shear walls
overhangs or other irregularities of plan that distribute the weight of the building unevenly or concentrate load on particular parts of it
the presence of a 'soft-storey' open ground floor which concentrates the load above columns that cannot support it during seismic deformation
poor connections between beams and columns, especially how the steel reinforcing bars are bent in
lack of proper hooks at the end of rebars on concrete joints
use of smooth rebars
the quality of the foundations and the liquefaction, landslide or subsidence potential of the underlying ground
poor state of maintenance of the structural elements of the building
any subsequent modifications to the original construction (e.g., superelevations).
The earthquakes chart a map of illegal and ineffective construction methods. Relatively few Turkish mass media openly discuss this (exceptions are KSL-NewsRadio and Bianet), and those that do are at risk of being treated as criminals. Nevertheless, the only way for reconstruction to succeed is for there to be a radical change in Turkish policy towards building practices. The issuance of a hundred prosecution notices to builders and engineers is a somewhat hypocritical response, given the amnesty they enjoyed. It shows that political responses to disasters depend on the electorate’s short memory.
Finally, there is a seismic hazard map of the area affected by these earthquakes. It was made in 1967. No one can say that the risk was not well known, or that the events were unexpected.