Abstract
An application for a quick earthquake damage scenario assessment is here presented as a potential tool for planning prevention actions or managing seismic emergencies in the volcanic region of Mt. Etna (Italy). As case-study, we considered the December 26, 2018 earthquake that, with a magnitude MW 4.9, represents the largest event occurring in the area during the last 70 years. The QUEST working group (the INGV macroseismic team) carried out a detailed survey in the damage area, collecting data on the number of buildings in the different vulnerability classes and related damage, with the aim to assign intensity. The maximum intensity reached degree VIII EMS along a narrow strip extending for 5 km astride the Fiandaca fault. In this paper, we simulated the damage scenario in the most struck municipalities of the epicentral area by testing different methodological approaches proposed in the literature using the information of the ISTAT census data collected by the Italian Institute of Statistics. We evaluated the damage level of the residential buildings and we validated the results comparing with the real damage data recognized in the field. Our analysis highlighted the difficulty of applying methods calibrated for larger earthquakes in tectonic domains, to small magnitude events in volcanic zones, where some operating assumptions must be introduced. Despite this, the results confirm the potential of the simulations based on statistical damage assessment methods also in these peculiar conditions, opening the way to finalized plans of pre- and post-earthquake interventions.
Highlights
Risk scenarios in volcanic areas are mostly referring to damage or disruption caused by lava flows, tephra fallout, or pyroclastic flows, i.e., in general to the eruption effects
In Italy, the analyses carried out at Vesuvius and Campi Flegrei are an example of the proper way to face the problem (Working Group, 2013) and are at the basis of the emergency plans issued by the Italian Department of Civil
In the study by Zuccaro and De Gregorio (2019), for instance, the damage expected from pre-eruptive seismic activity is evaluated with a uniform seismic input on the whole area, but not considering the characteristics of the attenuation of ground shaking in a volcanic area
Summary
Risk scenarios in volcanic areas are mostly referring to damage or disruption caused by lava flows, tephra fallout, or pyroclastic flows, i.e., in general to the eruption effects. Dolce et al, 2020) and to obtain a comparison of results, in the present work, we use three damage models in their original form, based on macroseismic intensity as a input parameter and respecting the philosophy on which the models were created and validated In this way we avoid resorting to intensity vs acceleration conversion laws that are affected by significant uncertainties, and considering local amplification effects (where present), already included in the macroseismic parameter. Allows verifying how damage models set for different seismotectonic contexts may depict the damage level caused by a volcanic earthquakes To this end, the validation process is based on real damage data collected in a detailed macroseismic survey throughout the damage area (Azzaro et al, 2020). The mode, on average, corresponds to the value of 65 ± 8% of the probability, a percentage in which the uncertainties are confined between –0.5 and + 0.5 of intensity
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