A Positive Flower Structure Uncovered by InSAR Images of the 2025 Mw ∼6 Afghanistan Earthquake Sequence

Abstract On 31 August 2025 (UTC), an Mw 6.0 shallow thrust earthquake struck the southern Hindu Kush region of Afghanistan, followed by a largest aftershock (Mw 5.6) on 4 September. This earthquake sequence caused widespread damage and unusually high casualties. To investigate the seismogenic structure, we utilized Sentinel-1 Terrain Observation with Progressive Scans Synthetic Aperture Radar data for Differential Interferometric Synthetic Aperture Radar processing to derive the coseismic deformation fields of both the mainshock and aftershock. The results show that the maximum cumulative deformation reached 24.2 cm in the ascending track and 17.0 cm in the descending track in line of sight, with consistent trends moving toward the satellites. The optimal earthquake slip model reveals a set of conjugate thrust faults, including the mainshock segment F1 (north-dipping, peak slip ≈ 1.11 m) and the aftershock segment F2 (south-dipping, peak slip ≈ 0.99 m). Integrating the regional fault network with these newly resolved faults, we interpret the earthquake sequence as the reactivation of a positive flower structure, which is likely controlled by flexural bending processes of the Konar fault system, the major tectonic boundary of the local crustal block. A Coulomb failure stress change (ΔCFS) analysis shows that the mainshock had effective triggering effects on the following sequence. Meanwhile, positive ΔCFS has also been loaded in the bend segment of the Konar fault through the earthquake sequence, highlighting this region as a locus of elevated seismic hazard potential for future.