GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.2 GNGTS 2023 Fig. 1 – Schematic representation of the country-scale, urban-scale, and building scale (i.e. structural health monitoring) monitoring networks in terms of coverage area and density of nodes. Figure from D’Alessandro et al., (2019a). Urban seismic networks: capabilities The implementation of an urban-scale seismic network enables several tasks. In particular, in case of strong earthquakes the network could represent the core of an entire chain of actions: some of them start in the very aftermath of the earthquake detection and are crucial in the short-term (Fig. 2), some others are only performed later. Of course, the basic action is the detection and the early processing of the seismic signal recorded at the network nodes. By means of opportune algorithms, which do not necessarily include the accurate location of the event, urban networks may represent a decisive infrastructure to build reliable earthquake early warning systems, at least those based on the on-site approach (Satriano et al., 2011; D’Alessandro et al., 2020). On-site early warning systems are based on the detection of the P-wave arrivals using an automatic earthquake recognition procedure and the estimation of the intensity of the impending strong shakings in a few fractions of second. The warning can be issued before S-wave arrivals, taking advantage of the difference between the P and S waves velocities. Earthquake early warning systems can be implemented in existing urban scale networks, especially when they are already operating into strategic buildings which should be the priority structures for warning systems. Strategic buildings are identified owing to their function in case of emergency or their value in terms of exposed peoples (e.g. hospitals, schools, etc.). Another important action is the possibility to draw near real-time shakes maps at local scale just few minutes after the event (Fig. 2). A shake map is the representation of ground motion intensity following a significant earthquake. It is a seismologically based interpolation and combines