Risk analysis of the built environment: understanding strengths and weaknesses of both quantitative and qualitative methodologies

Strategies to protect built environment against natural disasters changed over the past decades to focus more broadly on the consequences for the community. Several quantitative and qualitative methods were proposed for risk assessment and estimation of losses, time and sources for the recovery. The suitability of those methods depends on the specific natural disaster and the build and social environment. Moreover, the definition of hazard, exposure, vulnerability and risk depends on the risk assessment level. In this work, a general framework for natural risk assessment at the community level is presented. Than it is customized for earthquake-induced soil liquefaction, which causes extensive damage on built assets and implying huge repair costs and delays of the community recovery, and tested on San Carlo district (Italy) case study, hit by such disaster in May 2012. The results demonstrate the limits of quantitative methods for risk assessment at community level and those of qualitative methods for risk assessment at geotechnical level.