Tepehan Rockslide: A large-scale earthquake-induced geological structure formed by Mw:7.8 Kahramanmaraş (Pazarcık) earthquake, Türkiye

earthquake-Abstract: Three devastating and powerful earthquakes hit the southeastern and eastern parts of Turkey and the northestern part of Syria in February of 2023, causing many earthquake-induced slope movements. One of these major mass movements is called the “Tepehan Rockslide”, which was formed by the first Mw: 7.8 earthquake on February 6 th , 2023 at Pazarcık (Kahramanmaraş) located in the Altınözü district of Hatay province. The rockslide involved the movement of Middle Miocene basement rocks that consist of clayey limestone, marl, and fine-grained clastic sedimentary rocks. The morphogenetic evaluation of the structure reveals that the Tepehan Rockslide is a very rapidly developed translational interrupted ridge type earthquake-induced large-scale rockslide or a large rock glide that was formed at a distance of 19 km from the surface rupture and 136 km from the earthquake epicentre. Field observations and centimeter-precise numerical data via high resolution Unmanned Aerial Vehicle (UAV) footage with a GNSS-RTK mounted module reveal that the approximately E-W oriented longest axis of the structure is 496 m, and the widest profile is 184 m, extending in N-S direction. The total moving mass has been calculated to cover ca. 71,000 m 2 surface area, with an average volume of at least 1.1 million m 3 and total a weight of 2.75 megatons. Comparisons made with its counterparts worldwide show that the Tepehan Rockslide is not a unique earthquake-induced slope movement by itself. However, it is the largest of the detected voluminous rockslide type slope movements formed in the region during the February 2023 earthquakes.