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We performed large-scale earthquake economic loss estimations for France and cost–benefit analyses for several French cities by developing a semiempirical, intensity-based approach. The proposed methodology is inexpensive and easily applicable in case of a paucity of detailed information regarding the specific regional seismic hazard and the structural characteristics of the building stock, which is of particular importance in moderate-to-low seismic hazard regions. The exposure model is derived from census datasets, and the seismic vulnerability distribution of buildings is calculated using data mining techniques. Several hypothetical, large-scale retrofit scenarios are proposed, with increasing levels of investment. These cities, in their respective reinforced states, are then subjected to a series of hazard scenarios. Seismic hazard data for different return periods are calculated from regulatory accelerations from French seismic zoning. Loss estimations for the original (non-reinforced) configuration show high levels of expected building repair and replacement costs for all time spans. Finally, the benefits in terms of damage avoidance are compared with the costs of each retrofit measure. Relatively limited strengthening investments reduce the probability of building collapse, which is the main cause of human casualties. However, the results of this study suggest that retrofitting is, on average, only cost-effective in the parts of France with the highest seismicity and over the longest time horizons.

We performed a seismic vulnerability assessment of the city of Constantine (Algeria) using the Risk-UE and datamining-based methods [association rule learning (ARL)]. The ARL method consists in establishing relationships between building attributes (number of stories or building age) and the vulnerability classes of the European Macro-seismic Scale, EMS98. This approach avoids the costly process of drawing up an inventory of building characteristics in the field, which often discourages the assessment of seismic risk initiatives in weak to moderate seismic-prone regions. We showed that the accuracy of the assessment is independent of the subset used for the learning phase leading to development of the Constantine vulnerability proxy. Considering only two attributes, the vulnerability assignment is equal to about 75%, reaching 99% if material is added to the attributes considered. Comparison of Risk-UE and ARL results revealed a reliable assessment of vulnerability, the differences having only a slight impact on the probability of exceeding the damage level computed by EMS98 or Risk-UE in Constantine. The results of this study suggest that the ARL-based vulnerability proxy is efficient and could be applied to the rest of Algeria.

In moderate-to-low seismic hazard regions, estimating the socio-economic consequences of an earthquake on the regional scale is a costly and difficult task. This study analyses existing global earthquake databases to build a loss flat file of 445 earthquakes since 1967 with a magnitude greater than 4.5. The flat file includes information on the social consequences (e.g. fatalities and injuries) and economic losses (e.g. direct and indirect costs, number of buildings destroyed or damaged). In this study, exposed population and GDP at the date of the earthquake complete the flat file information, estimated thanks to the exposed area computed with an empirical relationship derived from the ground motion footprint provided by USGS ShakeMap. Earthquake consequences have increased since 1967 and follow a non-stationary Poisson distribution with rate proportional to exposure. In order to assess the stationarity of the consequences, we assumed stationary losses and fatalities by normalizing consequences by the exposed wealth and population verified on a sub-set of earthquakes for which exact population is given by national census. The completeness of the flat file catalogue is compared to the international seismological catalogue, and we compute the annual rate of exceedance of human and direct economic losses relative to the exposed population and the associated GDP per capita. We show that, although the number of casualties and the absolute magnitude of losses increase as consequence of urban concentration, global losses, relative to effective exposure corresponding to macroseismic intensity of at least V, decrease. (Access to the flat file: https://www.isterre.fr/philippe-gueguen/earthquake-losses-database/ ).