A Study of the 1999 Kocaeli Earthquake

Abstract. Loss estimation from future earthquakes is of growing importance in planning earthquake
protection strategies in high-risk areas. Loss models based on the spectral displacement approach
are now widely used because of generally acknowledged deficiencies in earlier approaches using
macroseismic intensity or peak ground-motion parameters. However, there has been to date rather
little earthquake damage data by which the new generation of models can be assessed and which
can be used to calibrate the parameters involved. The availability of several detailed damage surveys
carried out following the 1999 Kocaeli earthquake in Turkey, provides a rare opportunity for such an
assessment. In this paper the losses which would be predicted from two different approaches to loss
assessment – one using predicted macroseismic intensity, the other using the spectral displacement
method – are compared with actual observed losses in the Kocaeli event at two different locations
where surveys were carried out. One of these sites was very close to the surface fault rupture (<3 km
distance), the other at a distance of about 4.5 km. It is shown that the predictive methods available
generally overestimated the losses at these distances, and a number of possible reasons for these
discrepancies are considered. The sensitivity of loss estimates to variations in the key parameters
governing the estimation in each case are explored, in particular with respect to modifications in
the parameters of the attenuation relationships and the vulnerability parameters. The implications of
these results for estimating future losses are discussed