A methodology for seismic loss estimation in urban regions based on ground-motion simulations

Seismic vulnerability assessment of residential buildings in regions of high seismicity is an interdisciplinary problem requiring major inputs from fields of seismology and earthquake engineering. The basic two components of loss estimation methods are information on regional seismicity and building stock. This study presents a realistic loss estimation methodology where the first component, input ground motions, is obtained from regional ground-motion simulations using the stochastic finite-fault technique. The second component, building vulnerability information, on the other hand, is taken into account using fragility analyses. Introducing the ground-motion intensity parameters obtained from simulations to the fragility curves, we obtain seismic loss distribution in a region. In this study, we demonstrate the loss estimation methodology with an application to three northwestern cities in Turkey (Duzce, Bolu, and Kaynasli) that experienced two major earthquakes (M (sub w) 7.4 and M (sub w) 7.1) in less than three months in 1999. We initially verify the methodology with comparisons of observed and estimated damage ratios for the 12 November 1999 (M (sub w) 7.1) Duzce earthquake. Later, we present the estimated damage ratios under scenario earthquakes in the region for a magnitude range of M (sub w) 5.5-7.5. M (sub w) 6.5 is predicted to be the threshold magnitude for the cities of Duzce and Kaynasli where more than 60% of the building stock experience moderate and heavy damage. Because Bolu is at a farther distance from the fault plane, less damage is estimated for M (sub w) 5.5-7.0 than those in the other centers. For M (sub w) 7.5, all three cities are predicted to experience substantial rates of heavy damage and collapse.