Earthquake risk assessment of the city of Zagreb, Croatia: recent advances

This paper summarizes the findings of the recent project “Earthquake Risk Assessment of the City of Zagreb”, initiated as a national pilot study to serve as a model for future earthquake risk assessments across Croatia and as a foundation for changes to national regulations planned for 2026. Prompted by recent earthquakes, this initiative plays a key role in disaster risk reduction and complements ongoing post-earthquake retrofit efforts. The main activities of the project are presented, focusing on its most critical component: the collection of building data required to develop a GIS building inventory database. Attributes are primarily based on the latest Global Earthquake Model building taxonomy. The outcome is a comprehensive database of buildings and population, serving as the foundation for an exposure model. The earthquake risk model is presented through its three main components: hazard, exposure and vulnerability. The risk assessment was carried out in the OpenQuake Engine, using building-by-building data, and the main risk metrics are presented. The evaluation of the official city evacuation routes, considering potential road blockages caused by building debris, is briefly discussed. The limitations of the model are explained and some recommendations for future work are provided. This project marks a significant advancement following two earlier, more limited national earthquake risk assessments, both of which highlighted a critical earthquake scenario involving Zagreb. The new risk model at the building level was created, which can serve as a solid foundation for future risk mitigation activities and as an example for similar urban areas worldwide.