Advanced seismic microzonation of a medium size city over a deep sedimentary basin: The case of Foggia (Southern Italy)

Seismic microzonation is a basic element for emergency planning and developing effective risk reduction strategies. An application is presented of a cost-effective advanced strategy for the seismic microzonation of a large settlement: the city of Foggia in Southern Italy. Available geological and geophysical data have been reinterpreted and integrated with inversion techniques in order to reconstruct the seismostratigraphic structure of the local subsurface. Numerical simulations have been considered to infer the impact of these configurations on the local seismic hazard by taking into account uncertainty affecting the subsoil configuration. It has been demonstrated that the depth of the reference seismic bedrock plays a crucial role in hazard assessment, but its identification becomes challenging in the presence of a deep sedimentary basin, such as in the case of Foggia. Unlike most previous seismic microzonation studies in Italy, this work addresses uncertainties in expected seismic amplification effects and by considering alternative reference seismic bedrock configurations. On this basis, peak ground acceleration relative to 475y return period has been estimated for the study area by accounting for site effects and relevant uncertainty in the frame of a coherent probabilistic approach.