Seismic hazard assessment based on the pre-dominant period after the February 6, 2023, Türkiye earthquake doublets: A case study of Hatay province

Türkiye is located in a highly active seismic region. The North Anatolian Fault Zone (NAFZ) and the East Anatolian Fault Zone (EAFZ) were formed due to the collision of the Arabian Plate with the Eurasian Plate, the resulting movement of the Anatolian block (to the westward). Due to these tectonic movements, highly destructive earthquakes often occur in the NAFZ and EAFZ.

The most destructive earthquake doublets of the last century occurred on February 6, 2023, along the EAFZ. The first earthquake, with a moment magnitude (Mw) of 7.7 (according to AFAD), occurred at 04:17 local time with its epicenter located near Pazarcık in Kahramanmaraş, Türkiye. Its focal depth was calculated to be 8.6 km. A second major earthquake with a magnitude of 7.6 occurred near Kahramanmaraş (specifically in Elbistan)  nine hours later. Its epicenter point was determined about 62 km from Kahramanmaraş. Its focal depth was calculated to be 7.0 km.  The earthquake doublets on February 6, 2023, in Pazarcık and Elbistan (Kahramanmaraş) caused devastating damage and loss of life across 11 provinces, particularly in Kahramanmaraş and Hatay.

This study aims to conduct a pre-dominant period based seismic hazard assessment for Hatay province following two major earthquake doublets on February 6, 2023, in Türkiye. For this purpose, we utilized earthquake data of various magnitudes recorded by 10 earthquake stations managed by AFAD, located around the center of Hatay. We selected the earthquakes (the S-Wave windows part) and created soil pre-dominant period curves by applying the Horizontal to Vertical spectral ratio method. Site classification for the region was determined based on the predominant period values identified by Zhao et al. (2006) (Z-6), Fukushima et al. (2007) (F-7), and Di Alessandro et al. (2012) (DA -12). The preliminary results, the site classification for station 3123 has been identified as CL-I, as references by DA -12, SC-I by Z-6, and SC-1 by F-7. According to site classification results, the Spectral Acceleration (SA) curves were calculated by using the Ground Motion Prediction Equation (GMPE) developed by DA-12 (based on the dominant period values). These estimated values were then compared with the design spectra outlined in the Turkish Building Earthquake Code (TBEC 2018) and different GMPE proposed by Akkar et al. (2014). Thus, the regional seismic hazard for Hatay province was assessed according to scenario earthquakes.