The 2025 Mw 5.8 Aheqi Earthquake, China: Blind-Thrust Rupture on an Orogen Basin Boundary Fault from InSAR Observations.
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| Title: | The 2025 Mw 5.8 Aheqi Earthquake, China: Blind-Thrust Rupture on an Orogen Basin Boundary Fault from InSAR Observations. |
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| Authors: | Sun, Kai1 (AUTHOR), Xie, Lei1 (AUTHOR) leixie_geo@csu.edu.cn, Fang, Nan1 (AUTHOR), Chen, Zhidan1 (AUTHOR), Zhou, Peng1 (AUTHOR) |
| Source: | Remote Sensing. Apr2026, Vol. 18 Issue 7, p1078. 20p. |
| Subjects: | Radar interferometry, Inversion (Geophysics), Earthquakes, Thrust faults (Geology), Shearing force, Orogenic belts, Earthquake hazard analysis |
| Geographic Terms: | China, Tien Shan |
| Abstract: | Highlights: What are the main findings? The coseismic deformation field of the 2025 Mw 5.8 Aheqi earthquake is clearly obtained from InSAR data after tropospheric delay mitigation, showing maximum uplift of approximately 5.0 cm and 6.0 cm in the ascending and descending tracks, respectively, and indicating a thrust faulting mechanism. Bayesian inversion of InSAR data for the Aheqi earthquake reveals two possible fault models: a south-dipping back-thrust or a north-dipping thrust; the latter is preferred based on an integrated analysis of structural development conditions, surface deformation patterns, and local topography. The preferred fault model was loaded by >2 bar of Coulomb stress from the 2024 Wushi earthquake. What are the implications of the main findings? The dip ambiguity in the InSAR modeling of the Aheqi earthquake underscores that InSAR-based geometric solutions for moderate blind-thrust earthquakes necessitate the integration of structural and geomorphic analyses. Sequential rupture potential between reactivated and present-day active structures is evidenced by Coulomb stress loading between the geometrically distinct 2024 Wushi and 2025 Aheqi earthquakes, necessitating updated hazard models for southern Tianshan orogen. On 4 December 2025, nearly two years after the 2024 Mw 7.0 Wushi earthquake, an Mw 5.8 event struck the nearby county of Aheqi, southwestern Tianshan. Owing to the subparallel strikes of both nodal planes and the interspersed hypocenter locations among regional structures in the reported focal mechanisms, the exact fault geometry of this event remains unresolved, impeding a better understanding of regional tectonic activity and the associated seismic hazards. To resolve this, we applied Interferometric Synthetic Aperture Radar (InSAR) technique to map the coseismic deformation and invert for the fault geometry and slip pattern. Significant tropospheric delays are mitigated using a moving-window linear model and a multi-interferogram weighted averaging strategy. The result shows significant uplift (~5.0 cm for ascending track and ~6.0 cm for descending track), indicating thrust-dominated mechanism. Bayesian inversion reveals two possible fault models: a 31.6° north-dipping blind thrust or a 54.4° south-dipping back-thrust. While both fault planes fit the InSAR observations, integrated evidence from the absence of back-thrust development conditions, the surface deformation pattern, and regional topography indicates that the north-dipping Aheqi fault is the causative structure. Together with the steeper Maidan fault to the north, it forms the Orogen Basin boundary along the southern Tianshan piedmont. Our findings highlight that resolving moderate blind-thrust seismogenic structures using InSAR requires integration with pre-existing structural and geomorphic evidence. Furthermore, Coulomb stress calculations indicate a rupture-promoting effect from the Wushi earthquake, which occurred on a reactivated fault, onto the Aheqi event, with stress loading exceeding 2 bar at the hypocenter. Thus, the potential for stress-driven sequential rupture between reactivated and present-day active structures necessitates an updated seismic hazard assessment in the southern Tianshan. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | Highlights: What are the main findings? The coseismic deformation field of the 2025 Mw 5.8 Aheqi earthquake is clearly obtained from InSAR data after tropospheric delay mitigation, showing maximum uplift of approximately 5.0 cm and 6.0 cm in the ascending and descending tracks, respectively, and indicating a thrust faulting mechanism. Bayesian inversion of InSAR data for the Aheqi earthquake reveals two possible fault models: a south-dipping back-thrust or a north-dipping thrust; the latter is preferred based on an integrated analysis of structural development conditions, surface deformation patterns, and local topography. The preferred fault model was loaded by >2 bar of Coulomb stress from the 2024 Wushi earthquake. What are the implications of the main findings? The dip ambiguity in the InSAR modeling of the Aheqi earthquake underscores that InSAR-based geometric solutions for moderate blind-thrust earthquakes necessitate the integration of structural and geomorphic analyses. Sequential rupture potential between reactivated and present-day active structures is evidenced by Coulomb stress loading between the geometrically distinct 2024 Wushi and 2025 Aheqi earthquakes, necessitating updated hazard models for southern Tianshan orogen. On 4 December 2025, nearly two years after the 2024 Mw 7.0 Wushi earthquake, an Mw 5.8 event struck the nearby county of Aheqi, southwestern Tianshan. Owing to the subparallel strikes of both nodal planes and the interspersed hypocenter locations among regional structures in the reported focal mechanisms, the exact fault geometry of this event remains unresolved, impeding a better understanding of regional tectonic activity and the associated seismic hazards. To resolve this, we applied Interferometric Synthetic Aperture Radar (InSAR) technique to map the coseismic deformation and invert for the fault geometry and slip pattern. Significant tropospheric delays are mitigated using a moving-window linear model and a multi-interferogram weighted averaging strategy. The result shows significant uplift (~5.0 cm for ascending track and ~6.0 cm for descending track), indicating thrust-dominated mechanism. Bayesian inversion reveals two possible fault models: a 31.6° north-dipping blind thrust or a 54.4° south-dipping back-thrust. While both fault planes fit the InSAR observations, integrated evidence from the absence of back-thrust development conditions, the surface deformation pattern, and regional topography indicates that the north-dipping Aheqi fault is the causative structure. Together with the steeper Maidan fault to the north, it forms the Orogen Basin boundary along the southern Tianshan piedmont. Our findings highlight that resolving moderate blind-thrust seismogenic structures using InSAR requires integration with pre-existing structural and geomorphic evidence. Furthermore, Coulomb stress calculations indicate a rupture-promoting effect from the Wushi earthquake, which occurred on a reactivated fault, onto the Aheqi event, with stress loading exceeding 2 bar at the hypocenter. Thus, the potential for stress-driven sequential rupture between reactivated and present-day active structures necessitates an updated seismic hazard assessment in the southern Tianshan. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 20724292 |
| DOI: | 10.3390/rs18071078 |
