An Evaluation of Site Classification for National Strong-Motion Recording Stations in Turkey

Since 1976, the General Directorate of Disaster Affairs of Turkey has deployed several strong-motion accelerographs at selected sites, particularly along the North Anatolian Fault zone. Within the framework of the project entitled Compilation of National Strong Ground Motion Database in Accordance with International Standards, initiated in 2006, site conditions at a total of 153 strong-motion sites were investigated within the upper 30 m depth through boreholes including Standard Penetration Testing (SPT) and surface seismics. A preliminary assessment of the site characterization was held by making use of the mean shear-wave velocity of the uppermost 30 m depth with reference to the NEHRP provisions. The recorded accelerograms and corresponding catalogue information were compiled for these strong-motion sites using the available information from national and international databases. The 5% damped normalized elastic acceleration spectra of the accelerograms recorded for events with M_w ⩾ 4.0 were computed and categorized according to the site class and M_w. Mean normalized spectra computed for different M_w and site class bins were compared in order to investigate the significance of site class on the spectral response. NEHRP site classification is evaluated within the limitations of available data and findings.