In this paper, the M(w)7.2 Duzce earthquake is examined thoroughly with special emphasis on fault normal (FN) and fault parallel (FP) components and response spectra. For the spectra obtained from Istanbul, the seismic demands are highest in the Fatih and Zeytinburnu districts and lowest in the Maslak district. The consequences of the signal processing with Butterworth filters are investigated for various records of the Duzce earthquake. For this purpose, a complete strong-motion signal processing toolbox is developed that can process the data with alternative techniques. The current Turkish Earthquake Resistant Design Code (TERDC) does not take the near fault effects into account. New design response spectra for Turkey are proposed based on a previous attenuation relationship of the authors on 301 horizontal accelerograms from different earthquakes and according to the FEMA 356 specifications. The proposed design response spectra may be considered for implementation in important engineering structures since it accounts for distance and site effects. (c) 2006 Elsevier Ltd. All rights reserved.