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The seismic liquefaction is often responsible for the major part of the economic losses caused by earthquakes. Usually damages involve the foundations of buildings, bridges, embankments, underground constructions and are widely diffused over the cities. The strategies for the mitigation of risk aim to evaluate susceptibility and hazard on given areas by quantifying the liquefaction potential indexes from the results of fast investigations. The empirical relations proposed in the literature based on the results of cone penetration tests CPT, allow to calculate the indexes at each vertical, which can be reductive for the complete risk assessment of larger territorial extension. The present study moves at two distinct levels, one carried out with traditional geographic information systems aiming to map the liquefaction hazard over the territory, the second one aiming to define the three-dimensional distribution of the liquefiable deposit in the subsoil. The analysis focuses on the district of San Carlo, in the municipality of Sant’Agostino (Italy), located near the epicenter of the 2012 Emilia Romagna earthquake (Mw = 6.15). Several dozens of CPT profiles have been processed to compute the liquefaction potential maps and the individuation of the liquefiable deposits, using geostatistical methodologies. The results, validated with the observations of ground failures and damaged buildings recorded after the earthquake and with the geological structure of the investigated area, improve the quality of Microzonation studies with the addition of the liquefaction hazard and helps to precisely identify the susceptible subsoil deposit., http://papers.16ecee.org/files/16ECEE%20Spacagna%20et%20al.pdf

Seismic risk analysis and management of civil infrastructure systems has undergone an increasing interest among researchers in the recent past. Different methods and approaches have been proposed mainly dealing with the earthquake response of buildings and lifelines. Concerning transportation networks, most of the efforts focuses on the response of bridge stocks to specific earthquake scenarios, but very few examples exist examining the response of transportation networks as a whole. In particular, methods taking into account local site effects induced by liquefaction of the foundation soil are not developed yet. In this paper a novel framework is proposed to estimate the risk given by liquefaction on a road network within the more general EU project Liquefact. The study combines geotechnical analyses and the assessment of the traffic conditions to define hazard, vulnerability and exposure of the transportation network. The methodology has been applied to a rural area located in the district of Terre del Reno (Emilia Romagna, Italy) struck in 2012 by a seismic sequence that produced extensive liquefaction. The micro-zonation of liquefaction potential and the modelling of the transportation network are coupled to assess risk and identify mitigation strategies.

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.

International audience

A detailed and comprehensive assessment of risk is the basis to protect communities and assist decision-making towards the sustainable management of territories. For liquefaction this process implies to simultaneously investigate seismic hazard, susceptibility of the subsoil, vulnerability of structures, economic and social relevance of critical infrastructures and ultimately build a comprehensive multi-level model that considers the interaction among all aspects. Developing a methodology to achieve this goal is the scope of Liquefact, a EU H2020 project. A case study pervasively affected by liquefaction damages is here studied as a real scale scenario to identify the main factors of uncertainty. The available data concerning seismic motion, subsoil and building characteristics, damage and economic loss are used to develop a methodology aimed at quantifying and reducing uncertainties in the spatial distribution of risk.