Empirical predictive model for seismic damage of historical churches

Generally, strong seismic events cause serious damage to cultural heritage, especially in ancient churches characterized by a high vulnerability due to the intrinsic peculiarities of their structural systems which are not able to develop efficient resisting mechanisms. Starting from observed damage of churches and recorded ground motions, it is possible to define empirical response models. In this paper, an empirical predictive model for the seismic damage of churches is proposed. In particular, the damage is expressed by a continuous index and the seismic action is described by a scalar intensity measure. A sample of churches falling into a limited area hit by the Central Italy 2016 seismic sequence, which caused notable damage to the cultural heritage, has been chosen to calibrate the parameters of the proposed predictive model. The considered sample covers a wide range of damage and intensity levels, and includes all the churches of the area. The parameters of the model have been evaluated using the maximum likelihood estimation, considering a double step in the optimization procedure that combines a discrete with a continuous approach. Alternative proposals have been considered for the shape functions used in the numerical approximation and the results are discussed. Finally, the predictive model is applied to evaluate the damage scenario after a single seismic event and to illustrate the potential application of this risk analysis in decision-making processes. In particular, a deterministic event of magnitude 5.9 generated by the Senigallia fault has been considered and the consequences on historical churches reported in the national catalogue, are evaluated