Site-Dependent Spectra Derived from Ground Motion Records in Turkey

The current spectral shapes in the Turkish Seismic Code (TSC) are based on broadly described geological conditions, ignoring fault distance or magnitude dependencies on spectral ordinates. To address this deficiency, a data set created from a suite of 112 strong ground motion records from 57 earthquakes that occurred between 1976 and 2003 has been used to develop horizontal attenuation relationships for Turkey. This way it is possible to construct hazard-consistent design spectra for any national seismic region. The results are compared with the site-dependent spectral shapes of the Uniform Building Code (UBC) and the current TSC. It is shown that corner periods are consistent with those of UBC. TSC yields wider constant spectral acceleration plateau. Design spectra in both of these documents are conservative if the ground motion library that we used in deriving the spectral shapes is taken as representative. The results of this study enable site-distance–magnitude-specific design spectra suitable as a tool both for deterministic (scenario earthquakes) and probabilistic seismic hazard assessments.