Geomorphic evolution in response to active normal faults along the front of Wulashan, North China: Evidence from fluvial geomorphology and fault displacements

Quantitative analyses of tectonic processes and geomorphic development can provide insights into the formation and growth of boundary faults and associated geomorphic features. This study focuses on the Wulashan area, which is situated in the northern Ordos Block in North China. By integrating fluvial geomorphic indices with cumulative displacement along the Wulashan Piedmont Fault, we evaluate the fault’s influence on geomorphic development along the margin of the active block. The spatial patterns of geomorphic metrics suggest that the Wulashan area is currently in a mature landform evolution stage. Watershed morphometric analysis has revealed marked drainage asymmetry and an overall eastward tilt, accompanied by a nonequilibrium drainage divide, indicating that the region’s landscape continues to be modified by ongoing tectonic deformation. Using airborne LiDAR data, 240 displacements were obtained along the fault. The long-term cumulative offsets display a segmented, asymmetric, arcuate distribution pattern that closely mirrors the regional topography. In contrast, the ≤ 12 m cumulative offsets are higher and more consistent in the central fault segment, gradually decreasing toward both ends. The integration of fault displacement, topographic profiles, and geomorphic indices across watersheds, and consistent spatial relationships highlight the significant influence of the segmentation, kinematics, and displacement magnitude of a normal fault on the formation and evolution of the Wulashan Fault.