A multi-level study for the seismic microzonation of the Western area of Naples (Italy)

This paper shows the results of a multidisciplinary research aimed at defining the seismic microzonation of the district Bagnoli–Fuorigrotta in the Western part of Naples metropolitan area, which is subjected to a significant urban requalification project. The area is located in a complex geological setting within an active volcanic field and seismic hazard is characterized by both tectonic and volcanic seismicity, which frequently affected the urban setting. Following the recommendations of National and International Guidelines, the microzonation of the area was carried out adopting a multi-level approach. The maps obtained by applying Grade I and II approaches were the starting points for the numerical prediction of the site response carried out within the Grade III approach. The results of linear and non-linear dynamic analyses were synthesized in terms of amplification factors of peak ground acceleration at surface, PGA, and Housner Intensity, this latter computed through two different period ranges, i.e. 0.1–0.5 s and 0.7–2 s. The above factors were finally mapped adopting a rational approach to extend the local values of the surface amplification to broader areas. The results of the dynamic analyses highlighted that the seismic response of the whole area is highly affected by soil non-linearity and that the amplification of the ground motion mainly depends on the depth of the seismic bedrock, rather than on the local variability of shallow soil layering.