2 Urban Seismic Risk Evaluation: A Holistic 3 Approach 4

11 Abstract. Risk has been defined, for management purposes, as the potential economic, social 12 and environmental consequences of hazardous events that may occur in a specified period of 13 time. However, in the past, the concept of risk has been defined in a fragmentary way in many 14 cases, according to each scientific discipline involved in its appraisal. From the perspective of 15 this article, risk requires a multidisciplinary evaluation that takes into account not only the 16 expected physical damage, the number and type of casualties or economic losses, but also the 17 conditions related to social fragility and lack of resilience conditions, which favour the second 18 order effects (indirect effects) when a hazard event strike an urban centre. The proposed 19 general method of urban risk evaluation is multi hazard and holistic, that is, an integrated and 20 comprehensive approach to guide decision-making. The evaluation of the potential physical 21 damage (hard approach) as the result of the convolution of hazard and physical vulnerability 22 of buildings and infrastructure is the first step of this method. Subsequently, a set of social 23 context conditions that aggravate the physical effects are also considered (soft approach). In 24 the method here proposed, the holistic risk evaluation is based on urban risk indicators. 25 According to this procedure, a physical risk index is obtained, for each unit of analysis, from 26 existing loss scenarios, whereas the total risk index is obtained by factoring the former index 27 by an impact factor or aggravating coefficient, based on variables associated with the socio-28 economic conditions of each unit of analysis. Finally, the proposed method is applied in its 29 single hazard form to the holistic seismic risk evaluation for the cities of Bogota (Colombia) 30 and Barcelona (Spain). 31 Key words: holistic approach, risk evaluation, seismic risk, socio-economic vulnerabilit