GNGTS 2022 - Atti del 40° Convegno Nazionale

356 GNGTS 2022 Sessione 2.2 • the currently developed Shakemap procedure uses predictive ground motion laws that have not been implemented for volcanic areas; • local ground motion amplification effects were observed at the IOCA station. For the reasons stated above, the Shakemaps of the 21 August 2017 Ischia earthquake do not allow to accurately represent the shaking due to the earthquake on the island [3]. They are essentially derived from the application of the attenuation law alone [4, 5] and represent a compromise, leading to an underestimation of the shaking in the epicentral area, but to a more correct estimate of the shaking of the rest of the Island, in agreement with the available macroseismic surveys [6]. Having observed the low accuracy of the shakemap, it was considered to produce acceleration maps by interpolating the macroseismic intensity distribution maps in each cell 250m x250m [7] (represented in Fig. 1) and using as acceleration-intensity conversion law of Faenza and Michelini (2010). The exposure. Exposure has been defined as the distribution of vulnerability of the ordinary buildings present in the investigated area. Based on typological characteristics, buildings are grouped by classes of behaviour towards seismic phenomena, called vulnerability classes. In the present work, four behavioural classes have been considered, indicated with the letters from A (worst behaviour) to D (best behaviour). The construction of the exposure model has made use of several data collection surveys through the compilation of typological forms: - The CARTIS form, that provides information for sectors, for the 6 municipalities of Ischia [8] ; - The CARTIS BUILDING for 2,000 buildings appropriately chosen within the areas identified in the CARTIS form referred to in the previous point; - The PLINIVS form for 3,000 buildings (about 10% of the island’s building aggregates). The analysis of the buildings has been conducted through expeditious visual survey and compilation of the Level I form for the collection of parameters that influence the seismic and volcanic vulnerability of the buildings. Fig. 1 - Map of seismic intensity of the seismic event of Ischia (21 August 2017).