Geomatics, Natural Hazards & Risk (Dec 2023)
Structural height, amplification and damages during the superficial earthquakes at Casamicciola, Ischia Island (2017), and Santa Venerina, Catania (2018), Italy
Abstract
AbstractA rapid method to assess the potential seismic risk of a building due to its height or, equivalently, to the number of stories above ground is described. It was applied, despite already existing studies in this regard, to two earthquakes, those of Casamicciola, Ischia Island, on 21 August 2017 and Santa Venerina, Catania, on 26 December 2018; although characterized by a moderate magnitude (Mw 4.0 and Mw 4.8) and short duration, they produced victims and considerable damage. Accelerometric recordings of seismic stations in the areas of the two earthquakes were acquired and the pseudoacceleration spectra and dynamic amplification factors of the ground were obtained from them. By inversion of the algebraic relation between a building’s elastic period of vibration T0 and its height H, the so-called ‘critical’ heights (and corresponding number of stories above ground) to which corresponded the ‘greatest’ dynamic amplifications were identified: buildings with a number of stories above ground equal to the ‘critical’ values were considered potentially more exposed to seismic risk. For verification of the method, ca. 200 buildings in the areas of the earthquakes were surveyed and the resulting damages were related to the number of stories above ground. The results showed that, even though the two earthquakes were of moderate magnitude and short duration, the amplifications of the ground (at Casamicciola equal to 3 for reinforced concrete buildings and 2.4 for masonry buildings; at Santa Venerina 2 and 1.7 respectively) produced appreciable accelerations in buildings with two stories above ground, which turned out to be the ones with the greatest damage. The principle underlying the method consists of rapid numerical calculations performed on the pseudoacceleration spectra of the ground. Therefore, in areas with historical seismicity where accelerometric recordings are available, it is possible to identify buildings with potential exposure to seismic risk based on the number of ‘critical’ stories above ground and to subject them to more careful controls.
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