Seismic Performance of the Kahramanmaraş Earthquakes: Ground Motion Prediction Models and the Role of Vertical Components

On February 6, 2023, two very large earthquakes occurred in Türkiye. These earthquakes occurred on the Eastern Anatolian Fault, one of the most active fault zones in Türkiye. After two earthquakes occurred 9 hours apart, with Pazarcık (7.7 Mw) and Elbistan (7.6 Mw) epicenters, 11 cities of the country were directly affected by the earthquake. In addition to a significant number of casualties, structural damage caused by the earthquake occurred. Ground motion prediction equations (GMPEs), in short, are used to estimate the impact/value that the acceleration/velocity/spectral parameters etc. of a wave moving from an earthquake source can create in a study area. With the help of these attenuation relations, various earthquake parameters can be estimated depending on distance. In this study, the peak ground acceleration (PGA) values obtained from the stations taking measurements during the Kahramanmaraş earthquakes were examined using 6 different attenuation relations valid for Türkiye. In the study, data from 105 different stations measured during the Kahramanmaraş earthquake were used. In addition, the vertical earthquake effect caused by the earthquake was evaluated in terms of Turkish seismic code conditions. Looking at the study results; The approach of ground classifications, the fact that the acceleration values of the Kahramanmaraş earthquake remained above the curves of the attenuation relations and the failure to consider different earthquake characteristics have shown that the current attenuation relations are weaknesses. It has been observed that earthquake data deviate in a certain distance region in all attenuation relations. The GMPEs generally did not show high agreement with the Kahramanmaraş earthquake data. For this reason, the situations that should be taken into consideration when preparing a new decay relationship are examined. Finally, it was concluded that the higher-than-expected vertical earthquake effects were not assessed correctly in the code and therefore the vertical acceleration spectra given in the code should be updated.