Geologic, Topographic, and Seismic Characteristics of Large Landslides Triggered by 2023 Kahramanmaras Earthquakes, Türkiye

Abstract

The devastating Kahramanmaras earthquake sequence occurred on February 6, 2023. Two main events, Mw 7.8 and Mw 7.5, occurred 9 hours apart, affected 11 cities in Türkiye, and affected an area of ∼90,000 km2. This was the strongest historical earthquake doublet of magnitudes above 7.5 ever recorded in this region, and the consequences were catastrophic. The earthquake doublet triggered more than 3,600 landslides. Among these landslides, 35 of them have an area greater than 50,000 m2. Here, we focus on those largest coseismic landslides and show that 21 of them are pre-event landslides reactivated during the earthquake. They concentrate along a 5km-wide buffer zone around the surface rupture. Approximately 90% of these large landslides are distributed along the western section of the Eastern Taurus Mountain Belt, which is highly deformed and results in numerous overthrusts extending for 50 to 100 km. The geologic units in this part of the Taurus Mountain Belt consist of sedimentary, metamorphic, and igneous autochthonous and allochthonous units. The spatial distribution of landslides closely coincides with the topographic differences. They mostly (>82%) occurred on hillslopes where local relief varies between 500 and 700 m, and slope steepness ranges from 20° to 45°. Our preliminary analyses also revealed a relationship between the fault rupture dynamics and the distribution of large landslides. In addition to the rupture dynamics and topographic contrasts in the area, vertical lithological differences and the long-term tectonic deformations affecting autochthonous and allochthonous units have primary controls on the distribution of large landslides triggered by this earthquake doublet.