Abstract

The seismic risk evaluation usually works with a fragmented concept of risk, which depends on the scientific discipline in charge of the assessment. To achieve an effective performance of the risk management, it is necessary to define risk as the potential economic, social and environmental consequences due to a hazardous phenomenon in a period of time. This article presents a methodology which evaluates the seismic risk from a holistic perspective, which means, it takes into account the expected physical damage and also the conditions related to social fragility and lack of resilience, which favour the second order effects when a hazard event strikes an urban centre. This seeks to obtain results which are useful in the decision making process for risk reduction. The proposed method for urban seismic risk evaluation uses the fuzzy sets theory in order to handle qualitative concepts and variables involved in the assessment, the physical risk level and aggravation level, related to the social fragility and the lack of resilience, are evaluated and finally a total risk level is determinate.

Abstract

This article contributes to the development and application of two latestgeneration methods of seismic risk analysis in urban areas. The first method, namely vulnerability index method (VIM), considers five non-null damage states, defines the action in terms of macroseismic intensity and the seismic quality of the building by means of a vulnerability index. The estimated damage degree is measured by semi-empirical functions. The second method, namely capacity spectrum based method (CSBM), considers four no damage states, defines the seismic action in terms of response spectra and the building vulnerability by means of its capacity spectrum. In order to apply both methods to Barcelona (Spain) and compare the results, a deterministic and a probabilistic hazard
scenario with soil effects are used. The deterministic one corresponds to a historic earthquake, while the probabilistic seismic ground motion has a probability of exceedence of 10% in 50 years. Detailed information on the building design has been obtained along
years by collecting, arranging, improving, and completing the database of the dwellings of the city. A Geographic Information System (GIS) has been customized allowing storing, analysing, and displaying this large amount of spatial and tabular data of dwellings. The
obtained results are highly consistent with the historical and modern evolution of the populated area and show the validity and strength of both methods. Although Barcelona has a low to moderate seismic hazard, its expected seismic risk is significant because of the
high vulnerability of its buildings. Cities such as Barcelona, located in a low to moderate seismic hazard region, are usually not aware of the seismic risk. The detailed risk maps obtained offer a great opportunity to guide the decision making in the field of seismic risk
prevention and mitigation in Barcelona, and for emergency planning in the city.