The 6 February 2023 Mw 7.8 Kahramanmaraş earthquake rupture at a crossroad in Türkoğlu: A case for path of least resistance for rupture propagation

Summary The February 6, 2023, Mw 7.8 Kahramanmaraş earthquake reactivated the East Anatolian Fault Zone (EAFZ) and involved surface rupture from the Amik Basin in south to the northeast of Çelikhan in north. Although the EAFZ continues southwest towards the Gulf of İskenderun across the Amanos Mountain Range (AMR) via the Türkoğlu–Osmaniye segment, the 2023 rupture instead followed the western margin of the Karasu Valley. Our analysis suggests that this deviation was governed by structural architecture of these two routes. While both routes involve similar rock units, the AMR is characterized by a massive, intact, and thicker crust that allowed the velocity-strengthening frictional properties of the basement to act as an effective barrier, arresting the rupture east of Türkoğlu. In contrast, the transtensional architecture of the Karasu Valley—evidenced by deep-seated extensional fissures and basaltic volcanism—represents a structurally dilated and thinner crust. This extensional setting neutralized the potential frictional resistance of the basement, providing a rheologically compliant path of least resistance for the 2023 rupture. The Türkoğlu–Osmaniye segment has not experienced a major event for about last 1 500 years and considering a slip rate of ~4.8 mm/yr, about 7 meters of slip deficit has accumulated. Furthermore, the 2023 earthquake loaded stress on the Türkoğlu-Osmaniye Fault. For these reasons, the potential for an M > 7 earthquake on this part of the EAFZ is high, necessitating urgent preparedness for a large earthquake in the region.