Seismic Levee System Fragility Considering Spatial Correlation of Demands and Component Fragilities

Abstract

Seismic levee performance is most readily computed for short segments having consistent geometry, soil conditions, and seismic demands. Spatial variations of seismic demands and of segment capacities significantly influence system risk, which is critical for flood protection because any segment failure within the system can cause inundation. We present a methodology to compute the probability of seismic levee system failure conditional on individual segment fragility and spatial correlations of demands and of capacities. Seismic demands are estimated from ground motion prediction equations; their correlation is available in the literature. Capacities and their correlation are derived from levee damage observations from a levee system in Japan shaken by two earthquakes. We find seismic capacities to exhibit positive correlations over shorter distances than for demands. System fragility is computed using Monte Carlo simulations where segment demand and capacity realizations are generated to account for spatial correlations. We find that the probability of system failure is lower than would be obtained under an assumption of no correlation and that damage probability increases as the number of components in the system increases.