PSI - Issue 44

Maria Polese et al. / Procedia Structural Integrity 44 (2023) 123–130

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Maria Polese et al. / Structural Integrity Procedia 00 (2022) 000–000

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1. Introduction

In line with the indications of (Decision No. 1313/2013/EU) of the European Parliament on the objectives for the Union Civil Protection Mechanism, particularly to fulfil and enhance prevention and the risk management process, as well as to improve resilience and planning for disaster prevention, preparedness and response, there is the need to perform regular risk analyses. Referring to cross-border disasters, the update for UCPM rules (REGULATION (EU) 2021/836) encourages the comprehensive risk management approaches that underpin prevention and preparedness, taking into account multi-hazard aspects. The development of harmonized transboundary risk assessments may be useful for the preparation of Civil Protection plans and/or Emergency plans at the level of local communities (e.g. municipalities or larger provincial districts) or even for broader cross-border areas when transnational planning for land use or investments in risk reduction is foreseen. In this framework, the BORIS project (GA 101004882 - UCPM 2020-PP-AG) focuses on the development of cross-border risk analyses referring to seismic risk, flood risk as well as multi-risk in the framework of a multilayer single risk assessment. Within the project, a shared methodology to perform harmonized cross-border single risk (seismic risk and flood risk) as well as multi-risk analyses is proposed. Such methodology will be applied in two pilot transboundary regions at the Italy-Slovenia and Slovenia-Austria borders. This paper presents the first results of seismic risk analyses for two municipalities at the Italy-Slovenia border, performed employing the harmonized approach developed in the project. 2. The methodology for cross-border seismic risk assessment A harmonized probabilistic seismic risk analysis methodology was developed for the application in the Italian Slovenian cross-border area. It comprises four models, i.e. the seismic hazard model, exposure model, vulnerability model and consequence model. The models were input into the risk integral according to the conventional performance-based earthquake engineering framework (Cornell and Krawinkler, 2000), thus obtaining time-based risk indicators, such as the expected annual loss in terms of human lives, usable buildings, and money. The focus was put on loss estimaton of residental building stock with an emphasis on people occupying those buildings. The models used in the risk integral were defined at the municipality scale, which is the most refined spatial scale at which the data is available in both neighboring countries in the considered transboundary area. The risk integral was also evaluated separately for each individual municipality. The time-based risk indicators obtained at the municipality level were then added together to obtain the overall time-based risk indicators at the level of the transboundary area. Special attention was paid to the cross-border harmonization of the models used in the calculation of risk. The harmonized models are presented in more detail in the following subsections. 2.1. Hazard model Official seismic hazard models are usually derived at the national level. When such hazard models are utilized in a transboundary area, cross-border coordination of results is needed due to several differences in hazard assessment methods and datasets used. An obvious solution is the use of the 2013 Euro-Mediterranean Seismic Hazard Model (ESHM2013) (Woessner et al., 2015), which covers the whole European territory. It provides a complete assessment of seismic hazard and associated uncertainties and was computed using the OpenQuake engine (Pagani et al., 2014). The model uses harmonized and homogenized data from national, regional and site-specific PSHAs from across Europe. As an updated hazard model, the ESHM2020 model, was recently proposed (Weatherill et al., 2020), the latter is used in this study for hazard calculation. This model was developed based on an enhanced ground motion database and innovative ground motion modelling and epistemic uncertainty consideration. The ESHM2020 model provides seismic hazard calculations for rock-equivalent outcrop motion. Therefore, the effects of local soil and other effects on ground motion intensity had to be considered by supplement models. In particular, local maps with Vs30 values were used to account for the local soil effects. Based on the Vs30 values, the amplification factors were determined by considering the guidelines from wdEN 1998-1-1 (CEN, 2019).