Comparing Loss Estimation with Observed Damage in a Zone of Ground Failure: A Study of the 1999 Kocaeli Earthquake in Turkey

The building losses in Adapazari following the 17 August 1999 Kocaeli earthquake are estimated for both ground-shaking and ground-failure induced damage and the predictions compared with field observations. The ground-shaking damage is estimated using the capacity spectrum approach and accommodating the results of a previously published calibration of this model. These results, which do not incorporate ground-failure damage, are compared to the observed damage patterns in Adapazari to illustrate the significance of not including the more complex ground failure component in a loss model for a region of high liquefaction susceptibility. A preliminary estimation of ground-failure-induced damage is then presented based upon the HAZUS (FEMA, 2003) default methodology. The benefits of these additional calculations to the overall loss model are assessed to provide some quantitative decision-making guidance for those producing loss estimation models. The findings suggest that the benefits of specifically incorporating ground failure into a loss model only start to be obtained if a detailed approach using in situ geotechnical data as well as adequate representation of building foundations is adopted. Otherwise, the additional input data required is not commensurate with the small potential refinement in the estimated losses, particularly considering the compounded uncertainties associated with the simplified approach.