Search

The significant potential for human and economic losses arising from earthquakes affecting urban infrastructure has been demonstrated by many recent events such as, for example, L'Aquila (2009), Christchurch (2011) and Tohoku (2012). Within the current practice of seismic loss estimation in both academic and industry models, the modelling of spatial variability of the earthquake ground motion input across a region, and its corresponding influence upon portfolios of heterogeneous building types, may be oversimplified. In particular, the correlation properties that are well-known in observations of ground motion intensity measures ( IMs) may not always be fully represented within the probabilistic modelling of seismic loss. Using a case study based on the Tuscany region of Italy, the impacts of including spatially cross-correlated random fields of different ground motion IMs are appraised at varying spatial resolutions. This case study illustrates the impact on the resulting seismic loss when considering synthetic aggregated portfolios over different spatial scales. Inclusion of spatial cross-correlation of IMs into the seismic risk analysis may often result in the likelihood of observing larger (and in certain cases smaller) losses for a portfolio distributed over a typical city scale, when compared against simulations in which the cross-correlation is neglected. It can also be seen that the degree to which the spatial correlations and cross-correlations can impact upon the loss estimates is sensitive to the conditions of the portfolio, particularly with respect to the spatial scale, the engineering properties of the different building types within the portfolio and the heterogeneity of the portfolio with respect to the types. [ABSTRACT FROM AUTHOR]

A new hazard model for Italy has recently been proposed; hazard maps have been produced for various return periods, allowing the values of peak ground acceleration (PGA) and spectral accelerations for response periods up to 2 s to be interpolated for each of the 8,101 Italian municipalities. The new model allows for a more refined definition of the hazard in each municipality as compared to the current use of a fixed spectral shape anchored to upper bound 475-year PGA values and scaling factors for different return periods. The aim of this work is to investigate, in a preliminary fashion, the implications that the adoption of the new return-period dependent hazard maps would have on design and assessment of structures. To this end, the seismic performance of reinforced concrete frames of varying height is evaluated assuming they were located in each of the 8,101 municipalities in Italy and the results obtained with the current and the new hazard model are compared. The new model is shown to result in lower seismic risk in the majority of the municipalities. [ABSTRACT FROM AUTHOR]