Tectonic geomorphology of the Sürgü Basin (Malatya-Doğanşehi̇r)

This study aims to reveal the tectonic geomorphological characteristics of the Sürgü Basin, which is located on the northern branch of the East Anatolian Fault Zone (EAFZ). The research area, covering approximately 240 km², lies to the south of Doğanşehir (Malatya) and to the west of Çelikhan (Adıyaman). Both morphometric indices and field observations were employed to analyze the basin. Using 12.5 m–resolution ALOS PALSAR Digital Elevation Model (DEM) data, quantitative analyses were performed within the ArcGIS 10.8 environment. Several morphometric indices, including stream length–gradient (SL), asymmetry factor (AF), hypsometric integral (HI), valley floor width–to–height ratio (Vf), basin shape index (Bs), mountain front sinuosity (Smf), and index of relative active tectonics (IRAT), were calculated and comparatively evaluated. The results indicate that tectonic activity within the basin varies from moderate to high. Morphotectonic evidence such as pressure ridges, offset streams, fault scarps, and exposed fault planes along the Sürgü Fault confirms the presence of active deformation in the region. The IRAT analysis shows that the northern sector, particularly around Ulubaba Hill, exhibits higher tectonic activity compared to the southern part. The findings support that the Sürgü Fault is a left-lateral strike-slip fault, as verified by both morphometric and field data. The study demonstrates that the morphotectonic evolution of the Sürgü Basin is directly controlled by the northern branch of the EAFZ, and that the basin's geomorphic development is largely governed by ongoing tectonic processes. The results are considered to have decision-support value for regional seismotectonic assessment and land-use planning.