Italy is highly exposed to natural geological risks; knowledge of the “significant and extreme” forces to which the nerve centers of the electricity system may be subjected is essential to ensure its safe operation, to identify risks and to propose improvements.

In the second year of the current three-year research period, investigations focused on the determination of characteristic parameters regarding soil response to seismic stresses in terms of local seismic amplification. New acquisition campaigns were carried out in 2 sites in Central Italy, Fonte del Campo (RI) and Bazzano (AQ). In addition, passive seismic signals for the areas of Senigallia (AN) and Riccione (RN), acquired in 2019, were processed. For each site, the set of experimental measurements was appropriately processed to obtain the local seismic amplification function expressed in terms of frequencies of interest for anti-seismic engineering (from 0.5 to 10 Hz). The results were integrated and compared with experimental measurements present in the bibliography to validate the methodology.

The seismological application created in 2019 was integrated with new earthquake data relating to the ISIDe seismic catalog. The application allows to seismologically characterize the sites, to study the seismic intensity effects on the territory and to define the response spectra of the ground, both according to the current Technical Construction Standards and to appropriate laws of attenuation for acceleration amplifications as a function of the distance and magnitude of the earthquakes of interest. An important step has been taken towards determining the vulnerability of some components of the electricity system with respect to a seismic event ( fragility function ), which depends on their structural characteristics and dynamic behavior. Structures with their own modes in the typical range of earthquake frequencies can show significant acceleration amplifications coming from the ground and, consequently, an increase in mechanical stresses and deformations. These aspects are significant for the electricity generation, transport and distribution system, since the effects of seismic motion, or the forces connected to the horizontal and vertical components, can cause critical issues in the provision of the service in emergency situations.