SINGLE STATION SIGMA FOR TURKISH STRONG MOTION STATIONS

Abstract eng:
As ground motion observations over long enough time periods are unavailable for majority of sites, most of the ground motion prediction equations have been derived using observed data from multiple stations and seismic sources, and standard deviations (sigmas) of these equations are related to the statistics of the spatial variability of ground motion instead of temporal variability at a single site (ergodic assumption). This is one of the major shortcomings of carrying out site specific seismic hazard assessment with currently available ground motion prediction equations. In this study, we explore the variability at single sites within Turkey, decomposing sigma into different components so that the various contributions to the variability can be identified. The period and magnitude dependent standard deviation values obtained for Turkey using the ergodic assumption is changing between 0.56-0.82 ln units [1]. When single stations are considered instead, standard deviation estimates are reduced by 20%. Through the restriction of the analysis to a particular seismic source (i.e. North Anatolian Fault zone), the standard deviation values obtained for Turkey by [1] are further shown to reduce by about 10-20% depending on the spectral period under consideration. Implications of these findings for the seismic hazard of Istanbul district are further discussed within the scope of this study.

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