Objective On 7th October 2023, an earthquake sequence consisting of four Mw 5.5+ earthquakes struck Herat, Afghanistan, marking it as the deadliest earthquake in the region over the last two decades. Determining the source parameters and slip distribution, and assessing the building damage are of great scientific significance for understanding the tectonic mechanism of the Herat fault system and ensuring efficient rescue work.
Methods First, the coseismic displacements of the 2023 Herat earthquake sequence was acquired using interferometric synthetic aperture radar (InSAR) based on the Sentinel-1 images. Second, the fault geometry and slip distribution are determined using the InSAR displacement field from ascending and descending tracks as a constraint, and the seismogenic fault is analyzed and discussed. Finally, a building damage proxy map (BDPM) was acquired based on the multi-temporal InSAR coherence change detection method.
Results The coseismic deformation occurred between the Herat Fault Zone and the Siakhubulak Fault Zone. The maximum line-of-sight displacements observed in the ascending and descending tracks were about 32.3 cm and 58.9 cm, respectively. The inversion results show that the coseismic dislocation is dominated by thrust faulting with a small amount of right-lateral slip movement, and the fault has not ruptured to the surface, showing a north-dipping orientation with a dip of 34°. The slip was concentrated at depths of 2-8 km with a maximum slip of about 2.5 m occurring at a depth of 5.3 km.
Conclusions Through comprehensive analysis of multi-source remote sensing data, it can be preliminarily determined that the seismogenic fault is an unmapped northward thrust fault on the north side of the Herat fault zone. The results of the BDPM indicate that the earthquake sequence caused relatively severe damage to buildings within 40 km of the epicenter, which may be the direct cause of the large-scale casualties caused by the event.
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