یک مدل بهبود یافته برای تخمین ریسک لرزه ای در پرتغال An improved model for seismic risk assessment in Portugal

1. Introduction The occurrence of natural hazards, particularly earthquakes, has been responsible over the years for the most devastating effects on human, environmental and economic losses in societies. Portugal has experienced destructive seismic events in the past, including the wellknown “Lisbon earthquake” in 1755, during which it is estimated that about 50% of the existing buildings have collapsed and 10% has perished (Silva et al., 2014). The projections of reinsurer Swiss Re (2011) for Portugal reveal a worrying scenario, estimating that the economic impact of an intense seismic event will exceed 25% of the gross domestic product, which is aggravated by the fact that percentage of assets that are insured against earthquake risk is virtually absent (less than 10%). The recognition of the inevitability of the seismic impact to the societies, even in countries with high level of economic and social development, shows how important it is to estimate the expected share of resources that would be affected in a given region. In this sense, it is manifestly urgent to estimate the human and economic losses. The results of such exercise will be capable of providing the various societal players with real and objective information society that supports the establishment of response strategies and better decision making. Despite the important past studies on seismic hazard (Vilanova and Fonseca, 2007) and seismic risk assessment that were carried out for Portugal (Campos Costa et al., 2009) there is still a long way towards the mitigation of seismic risk. Moreover, a significant percentage of existing Portuguese buildings were not seismically designed and many of those that were indeed seismically designed are not expected to exhibit adequate seismic performance. In this sense, there are few studies that have sought to characterize as accurately as possible the seismic vulnerability of the Portuguese in-built (Sousa et al., 2010), using models of different complexity levels capable of defining fragility functions for various building typologies (derived empirically, analytical or based on expert opinion). Other studies have also addressed the seismic vulnerability and risk assessment of Portuguese urban areas, focusing particularly on historic centres (Vicente et al., 2010; Ferreira et al., 2013; Maio et al., 2015; Lamego et al., 2016; Ferreira et al., 2016).