Blind thrusting and strain partitioning in northeastern Afghanistan: insights from the 2025 Mw 6.0 Asadabad earthquake

SUMMARY The Mw 6.0 Asadabad earthquake and its aftershock sequence, which occurred on 2025 September 1, in northeastern Afghanistan, provide an important window into the strain partitioning and blind thrusting mechanisms at the front of the Pamir–Hindu Kush orogen. Utilizing ascending and descending Sentinel-1 InSAR data, we precisely constrained the coseismic deformation fields and fault slip distributions of the sequence. Inversion results characterize the event as a typical blind thrust rupture with no observable surface rupture. The optimal fault model comprises three discrete thrust segments: during the mainshock, slip on the primary buried fault (F1) drove the rupture of a shallow secondary fault (F2), while the adjacent Mw 5.6 strong aftershock (F3) was triggered three days later via static Coulomb stress transfer. Integrating regional geological context with rock mechanics analysis, we propose that the high-strength metamorphic crystalline basement (marble and gneiss) governs the development of this buried blind thrust system, whereas the near-surface layer exhibits diffuse deformation. This study confirms that within the predominantly strike-slip Kunar fault system, secondary blind thrusts play a pivotal role in accommodating the compressive component of the India–Eurasia convergence. These findings underscore that in zones of diffuse orogenic deformation, the seismic hazard posed by cryptic blind faults is frequently underestimated and warrants prioritized attention in future risk assessments.