Coseismic Surface Displacements Derived From High-Resolution GF-7 Stereogrammetric Terrain Differencing: The 2025 Tibet Dingri Mw7.1 Earthquake

Coseismic displacement and deformation patterns near seismic rupture zones are crucial for understanding earthquake rupture processes, fault behaviors, and the relationship between active faults and topographic features. Recent advances in sub-meter accuracy digital terrain data derived from high-resolution optical satellite stereo imagery have provided new geodetic approaches for differential topography studies, including three-dimensional coseismic surface displacement field acquisition. This study generated pre- and post-earthquake topographic point cloud data (average point density: 1.2 points/m²) using GF-7 satellite stereo imagery, and obtained a 25-meter spatial resolution three-dimensional coseismic surface displacement field in the near-fault area of the 2025 Dingri, Tibet Mw7.1 earthquake through a window-based (50-meter window size) Iterative Closest Point (ICP) algorithm. The results reveal that the surface rupture of the Dingri earthquake was dominated by vertical displacement with insignificant horizontal motion, consistent with the focal mechanism solutions and field investigations of the rupture zone. The vertical displacement distribution extracted from ICP displacement field exhibits a "high central section with decreasing values northward and southward" pattern, reaching a maximum vertical displacement of ~2.5 m near the central Nixiacuo area, decaying to ~1.2 m northward and ~0.5 m southward. Compared with field measurements, ICP-derived vertical displacements generally exceed field observations, indicating that surface dislocation markers only reflect the minimum coseismic displacement along the rupture zone. The ICP method quantifies cumulative displacement across hundreds of meters on both sides of the rupture, providing critical constraints for studying shallow slip deficit mechanisms and facilitating future investigations of fault slip transfer processes from deep to shallow levels. This study demonstrates the unique advantages of new high-resolution optical satellites in long-term pre-seismic data accumulation, rapid post-seismic data acquisition, and comprehensive coverage of surface deformation zones. These capabilities enable timely construction of near-field 3D coseismic displacement fields, allowing differential topography techniques to measure 3D coseismic deformation in areas inaccessible for LiDAR surveys. This approach effectively compensates for limitations of conventional InSAR and sub-pixel correlation techniques near surface ruptures, where large deformation gradients or insensitivity to vertical displacements often cause measurement failures.