A simplified vulnerability model for the extensive liquefaction risk assessment of buildings

The quantitative assessment of natural risks offers a rational strategy to protect communities, undertake cost effective mitigation and plan the organic and sustainable development of urban systems. For cascade events such as earthquake-induced liquefaction, assessment implies to characterize and reconstruct the areal distribution of seismic hazard, subsoil susceptibility, physical vulnerability, economic and social relevance of structures and to combine all factors in a unitary predictive model. Considering that aleatory variability and epistemic uncertainty affect the characteristic variables and their mutual correlation, it is also necessary to quantify their influence on the prediction. Within this framework, a vulnerability model is proposed to comprehensively assess the physical damage of buildings in an urban system. A chain method is formulated combining calculation schemes recently introduced in the literature with ad hoc numerical analyses. The effectiveness of the method is tested comparing prediction with the effects observed in the city of Christchurch during the 22nd February 2011 earthquake. The unprecedented documentation available after this earthquake enables to validate different components of the model and disclose the importance of possible disregarded factors. A geostatistical methodology is proposed throughout the paper to process data, quantify and govern the different uncertainty factors.