Geomorphological Controls on The Distribution of Lateral Spreading Triggered by The February 6, 2023, Kahramanmaraş (Türkiye) Earthquake Sequence

On February 6, 2023, two earthquakes of magnitudes 7.8 Mw and 7.6 Mw occurred on the East Anatolian Fault zone, centered in Kahramanmaraş, Türkiye. These earthquakes caused widespread destruction, particularly in residential areas, and triggered lateral spreads that caused significant economic damage to agricultural lands. Within the earthquake-effective area, such landslides are more frequent along the Asi River in the south of Hatay. The banks of the Asi River have been a region where lateral spreading events are frequent due to morphological and sedimentological factors such as loose sandy soil and gentle slopes. This study aims to understand the distribution of lateral spreads triggered by the February 6 Türkiye earthquake sequence and the geomorphological conditions that affected this distribution along the 86 km section of the Asi River within Türkiye's borders. For this purpose, high-resolution satellite imagery, aerial photographs, and optical data collected via UAVs during fieldwork were processed using remote sensing software to produce mapping bases and conduct analyses. We mapped 328 lateral spreads in the earthquake-affected area. Along the Asi (Orontes) River, 238 lateral spreads were identified, constituting 72.6% of the total inventory of lateral spreads triggered by the earthquake doublet. The mapped lateral spreads in this area ranged from a minimum of 200 m² to a maximum of 100,000 m², with a total surface area of 3.5 km² exclusively along the Asi River. These earthquake-triggered lateral spreads demonstrated varying crack densities and deformation characteristics influenced by the meandering structure of the Asi River, which has a sinuosity index reaching up to 3.76. Lateral spreads were predominantly observed at point bars with higher sand content, where they moved horizontally towards the Asi River channel by a minimum of 1 meter and a maximum of 35 meters. We conclude that a deeper understanding of the frequency-magnitude relationships and spatial distribution patterns of lateral spreads enhances the development of regional susceptibility models and improves insight into the long-term geomorphic impacts of earthquakes, particularly concerning riverbank erosion.