GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 2.2 GNGTS 2024 different VMs and a preliminary vulnerability evaluation. However, the capability of existing VMs to represent effective susceptibility to damage must be tested with real damage data. To this end, data pertaining to the April 15, 1979, Montenegro Earthquake, referred to as the Seismic Event (SE), are considered. Ultimately, damage data extracted and revised from historical reports are used to calibrate a heuristic VM that suitably combines existing VMs for similar typologies. Damage data analysis In Montenegro, the data on historical earthquakes and relevant damages are not collected in systematic way and there is a lack of structural database which can provide information on events and direct effects of earthquakes. However, the SE left an indelible mark on the collective memory of Montenegrins, and a few initiatives were taken to assess the extensive damage caused by this catastrophic event. We rely on two of them: the historical Report IZIIS (Petrovski et al. 1984) and the work by Pavićević (Pavićević Božidar S 2004). In both reports, the classification of damage differs from the European Macroseismic Scale 1998 (EMS98) (Grünthal & European Seismological Commission 1998) notation. Therefore, following an approach similar to Rota et al. (Rota et al. 2008), we have developed the conversion scheme reported in Tab. 1. Usability Report IZIIS 84-085 (Petrovski et al. 1984) EMS 98 (Grünthal 1998) Usable 11 - no damage DS0 12 - no damage of LBS DS1 13 - damages of LBS DS1 Temporary unusable 21 - damaged LBS DS2 22 - heavy damages of LBS DS2 Unusable 31 - severely damaged DS3 32 - partially collapsed DS4 33 - collapsed DS5 Tab. 1 – Conversion scheme for damage levels into EMS98 damage states (DSs). Note: LBS stands for load-bearing system. The earthquake's hypocenter was located offshore, and the coastal municipalities suffered the most severe impact of the devastation. A shake map for this event is available from United States Geological Survey (USGS) (U.S. Department of the Interior 2023). In the present study, Peak Ground Acceleration (PGA) is selected as the Intensity Measure (IM). For the coastal cities a Modified Mercalli intensity (MMI) between VIII and IX was reported in (Blagojević et al. 2023); by adopting the I-PGA conversion law proposed in Trifunac et al. (Trifunac MD et al. 1991), a reasonable agreement of the corresponding PGA with the values from the USGS shake map can be observed. These shake map values are reported in Tab. 2.