Is the Turkish Design Spectrum Governed by Response at Two Periods Reliable?

This paper draws attention to apparent discord between spectra from actual recordings at a number of stations of the national strong motion network of Turkey with the design spectra for the same location and site characteristics. We find that, for deep basins with Site Class D or E profiles, the design spectrum seems not to recognize consistently the constant velocity and longer period demand. If this conjecture is true, it may foreshadow unsafe designs for the building stock in Turkey in similar environments. The recently recorded strong ground motion records from the 06 February 2023, M 7.7 and M 7.5 Kahramanmaraş, earthquakes support the conjecture of this study and provide evidence for a need to revise the corner periods of the design spectrum in the Regulation.