Tectono-geomorphic records of neotectonic activity along the Kachchh Mainland fault in a seismically active intraplate setting, Kachchh paleo-rift basin, western India

The Kachchh paleo-rift basin located in the western India stands out as one of the highly seismic intra-plate regions in the world, which falls under zone-IV (high risk) as per seismic zonation map of India. This study examines morphotectonic landforms within a broad deformation zone of the Kachchh Mainland Fault (KMF) to elucidate its neotectonic evolutionary history and associated seismic hazard. Morphometric analysis along the KMF indicates that approximately 47% of the 2800 km² study area exhibits neotectonic activity. By analyzing changes in strike-parallel and perpendicular river channel steepness through swath profiles, we identified seven distinct segments along the KMF. Our findings suggest diverse ground responses to steepness changes in each segment, which align well with geomorphic and geodetic data. Tectono-geomorphic investigations reveal the KMF as an oblique-slip fault, exhibiting both transtensional and transpressional movements. Optical chronology of tectonic landforms indicates ∼15 deformation episodes spanning the Late Pleistocene at 25 ka, 23 ka, 19.8 ka, 18 ka, 17 ka, and the Early Holocene at 10 ka, 8 ka, and 7 ka. Additionally, three Middle Holocene earthquake events at ∼ 5 ka, 4 ka, and 3 ka, and four Late Holocene earthquake events at ∼ 2 ka, 1.3 ka, and 870 years have been identified. Finally, we present an active fault map of the KMF zone by integrating all available data (geomorphologic, geodetic, and geologic) which will be useful for seismic hazard assessment across the region.