Seismic risk assessment at urban scale from 3D physics-based numerical modeling: the case of Thessaloniki

The main aim of this work is to present a prototype of seismic risk assessment study at urban scale which incorporates next generation tools for hazard assessment, with application to the city of Thessaloniki, Northern Greece. The key ingredient of the proposed approach is the characterization of earthquake ground motion by means of three-dimensional broadband physics-based numerical simulations, which explicitly account for the fault rupture, the propagation path in heterogeneous media and complex geological conditions. The seismic damage of contemporary reinforced concrete building stock of the city of Thessaloniki has been evaluated using the capacity spectrum method, for a scenario corresponding to the destructive historical earthquake of June 20th 1978 (MW 6.5). Although the vulnerability model considered in these analyses reflects the contemporary building stock and, hence, differs from the situation at the time of the earthquake, the soundness of our damage estimates has been successfully verified through the comparison with the post-1978 earthquake damage observations. Results of this study demonstrate that 3D physics-based simulations can provide a more accurate and detailed characterization of earthquake ground motion and of its spatial variability, as compared to standard empirical approaches, and can be effectively used to improve seismic risk studies for strategic urban areas.