Non-linear site response and liquefaction analysis of soil site in Kahramanmaras during the Mw 7.7 and Mw 7.6 Turkey earthquakes

In Turkey, one of the most important earthquake belts in Europe, two major earthquakes (Mw: 7.7 and 7.6) occurred about 8 h apart in Kahramanmaraş province on February 6, 2023. Located on the South Anatolian Fault Zone (EAFZ), Kahramanmaraş province and 10 surrounding provinces were affected by the earthquake, which killed approximately 50,000 people and injured approximately 250,000 people. When the cause of this effect was analyzed, it was determined that the building stock of the region was old, as well as the peak ground acceleration (PGA) values that occurred on the surface and to which the structures were exposed. In addition to structural problems, it has been determined that there are significant ground problems such as ground amplification and ground liquefaction in the geotechnical field. For this reason, it is necessary to accurately determine the spectral acceleration values, which show important parameters in the design of buildings, and to take necessary precautions by identifying problems such as soil bearing capacity, settlement problem, liquefaction, and soil amplification in advance. Turkey Building Earthquake Code (TEC 2019) entered into force in 2019. In this study, surface acceleration records exposed to the structures in the region were analyzed. Earthquake acceleration records were obtained from the stations closest to the epicenters of the earthquakes that occurred in Elbistan and Pazarcık in Kahramanmaraş province, and soil amplification analysis and liquefaction potential risk analysis were performed at 3 different points in Kahramanmaraş province. In addition, 11 earthquake acceleration records were selected from different parts of the world reflecting the earthquake characteristics of the region and the analysis was repeated and the design spectrum was compared with the data obtained from the field. Site-specific soil behavior analyses were performed in the study where the existing conditions of the structures in the region were also examined. The data obtained show that the regulation does not fully reflect the field in cases where the structures are exposed to high acceleration values on the surface due to the soil structure, at the same time, liquefaction problems are high and the structures have not undergone the necessary ground improvement processes.