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.