Holistic Evaluation of the Seismic Risk for Metro Manila

The urban seismic risk evaluation is proposed from a holistic point of view; that is, an integrated and comprehensive approach to guide decision-making. Evaluation of the potential physical damage (hard approach) as the result of the convolution of hazard and physical vulnerability of buildings and infrastructure is the first step of this method. Subsequently, a set of social context conditions that aggravate the physical effects are also considered (soft approach). In this method the holistic risk evaluation is based on urban risk indicators. According to this procedure, a physical risk index is obtained, for each unit of analysis, from existing loss scenarios, whereas the total risk index is obtained by factoring the former index by an impact factor, based on variables associated with the socio-economic conditions of each unit of analysis.

This method developed by Carreño, Cardona and Barbat for urban risk evaluation is based on Cardona’s model and uses a holistic approach and describing seismic risk by means of indices. Expected building damage and losses in the infrastructure, obtained from future loss scenarios are basic information for the evaluation of physical risk in each unit of analysis. Starting from these data, a physical damage index is obtained.2 The holistic evaluation of risk by means of indices is achieved affecting the physical risk with an impact factor, obtained from contextual conditions, such as the socioeconomic fragility and the lack of resilience, that aggravate initial physical loss scenario. Available data about these conditions at urban level are necessary to apply the method. This approach contributes to the effectiveness of risk management inviting to the action identifying the hard and soft weaknesses of the urban centre.