Recent advances in seismic vulnerability assessment of Croatian coastal urban area

The seismic vulnerability assessment of existing urban areas provides fundamental information about reducing seismic risk in different phases of planning and emergency management. This contribution presents recent advances in seismic vulnerability assessment in Croatian coastal areas at various scales, starting with a detailed analytical approach at the building scale to large-scale evaluation at the building level and the level of the homogeneous zones. The investigation was performed in the town of Kaštela. This typical coastal settlement has expanded over past centuries, resulting in a heterogeneous distribution of the buildings built in periods with different technical regulations. A detailed nonlinear-linear analysis of important buildings (historical, public) has been performed providing evidence of their collapse behaviour. A comprehensive hybrid approach to large-scale seismic risk assessment, combining seismic vulnerability indices with critical PGAs for different limit states, has been applied to define vulnerability curves that relate vulnerability index, damage index, and peak ground acceleration. The outcome of the present analysis is the large-scale risk representation in terms of the damage and seismic risk indexes at the building level. The level of seismic risk to the community depends on several other parameters whose activation reduces the resilience to extraordinary events. Considering the characteristics of the observed pilot site, additional criteria for the risk assessment of homogenous zones are introduced, such as communal infrastructure, road network, construction density, inhabitation density, importance factor (public building, school, etc.), and status of protected historical buildings. The proposed methodology addresses seismic risk assessment at the level of homogeneous zones and utilizes Spatial Multi-Criteria Decision Making and PROMETHEE method. The presented approach to seismic risk assessment has important operational outcomes in the seismic risk management of the investigated area.