Abstract

The risk evaluation model CAPRA (Comprehensive Approach to Probabilistic Risk Assessment) is a techno-scientific methodology and information platform, composed of tools for evaluating and communicating risk at various territorial levels. The model allows evaluating losses on exposed elements using probabilistic metrics, such as the loss exceedance curve, the expected annual loss and the probable maximum loss, useful for multi-hazard risk analyses. In this article, the process of probabilistic seismic risk analysis is described, explaining the main features of the CAPRA modules of hazard, vulnerability and risk estimation applied to the city of Barcelona, Spain. In addition, according to the physical risk results and the information on the socioeconomic indicators of the city, this article presents the holistic evaluation of seismic risk, which is a valuable result to facilitate the integrated risk management by the different stakeholders involved in risk reduction decision making.

Abstract

This monograph explains how probabilistic seismic risk assessments can be performed at different resolution levels using the same methodology, providing results in terms of the same metrics; but it also highlights what the differences in terms of inputs for the analysis are in the different cases. A country level assessment is first performed using a coarsegrain exposure database that includes only the building stock in the urban regions of Spain. A detailed urban seismic risk assessment is performed for Lorca, Murcia, Spain. In both cases, the fully probabilistic seismic risk results are expressed in terms of the loss exceedance curve, which is the main output, from where different probabilistic risk metrics, such as the average annual loss and the probable maximum loss can be derived. Because of the damage data availability for the Lorca, May 2011, earthquake, a comparison between the observed losses and those modelled using an earthquake scenario with similar characteristics in terms of location, magnitude and spectral accelerations was done for the building stock of the city. The results of the comparison are presented in terms of expected losses (in monetary terms) and damage levels related to the obtained mean damage ratios are compared with those observed by post-earthquake surveys. This monograph is an effort to explain, in a transparent and comprehensive way, through a step by step example, how risk can be calculated in probabilistic terms and what are the influences of the inputs in each of the stages and what the obtained results mean. After reviewing several available tools to estimate catastrophe risk by means of probabilistic approaches, the CAPRA Platform was chosen because its flexibility, compatibility with the assessments to be performed at different resolution levels and its open-source/freeware characteristics.

Abstract

Disaster risk is not only associated with the occurrence of intense hazard events but also with the vulnerability conditions that favour or facilitate disasters when such events occur. Vulnerability is closely linked to social processes and governance weaknesses in disaster-prone areas and is usually related to a set of factors of fragility, susceptibility, and lack of resilience of the exposed human settlements. The holistic risk assessment aims to reflect risk from a comprehensive perspective by using, in one hand, the physical risk or potential physical damage directly linked to the occurrence of hazard events and, on the other hand by capturing how underlying risk drivers or amplifiers –social, economic, environmental factors, non-hazard dependent elements, may worsen the current existing physical risk conditions in terms of lack of capacity to anticipate or resist, or to respond and recover from adverse impacts. This article presents the results of the holistic evaluation obtained at subnational level in Colombia in the framework of the Risk Atlas of Colombia of the National Unit for Disaster Risk Management, UNGRD. The evaluation was performed using the probabilistic physical risk results obtained in the multi-hazard risk assessment and 16 socio-economic indicators available for 1,123 municipalities of Colombia. These results are useful to identify risk drivers that are associated not only to the physical vulnerability of the buildings and infrastructure but also to social issues that should be examined and tackled in a comprehensive way.