Abstract:

On January 30, 2024, an M_W7.0 earthquake struck the Wushi region of the southern Tianshan Mountains, Xinjiang, China. This earthquake, located in a tectonically active zone dominated by intense crustal shortening and thrust faulting, providing a valuable opportunity to investigate fault geometry and rupture mechanisms in the region. We utilized Sentinel-1 InSAR data combined with advanced inversion techniques to analyze the coseismic deformation field, determine fault parameters, and explore the spatial relationship between the mainshock and aftershocks.
High-resolution coseismic deformation fields were generated using D-InSAR processing of Sentinel-1A ascending and descending orbit data. Nonlinear inversion methods were employed to calculate fault geometry and sliding distribution, with both single-fault and dual-fault models tested to accommodate the complex faulting characteristics. Residual analysis was performed to examine the relationship between the mainshock and the M_W5.7 aftershock, and geological surveys were used to validate fault models and rupture characteristics.
The maximum line-of-sight(LOS)displacement of the coseismic deformation field reached 70cm, displaying an elliptical pattern along the Maidan Fault. The dual-fault model revealed significant geometric complexity: the fault strike rotates clockwise by 20°~25° east of the epicenter, and the dip angle decreases from 60° in the west to 40° in the east. Fault slip was primarily concentrated west of the epicenter, characterized by high-angle thrusting with a left-lateral component, while slip in the eastern segment was lower in magnitude and relatively dispersed. The overall distribution exhibited shallow slip deficit. The correlation between geometric variations and sliding distribution suggests the presence of a geometric barrier east of the epicenter, acting as an obstacle to rupture propagation. The coseismic rupture was confined between the Yushanguxi River and the Wushi depression, with fault steps and structural complexities on the eastern and western boundaries limiting the rupture extent. The M_W5.7 aftershock produced a clear LOS deformation field, with the fault strike deviating by ~10° from the mainshock trace and dipping southeast. The surface trace of the aftershock fault closely aligned with mapped surface ruptures, and the shallow slip magnitude matched the observed vertical offsets from geological surveys.
We also demonstrates that fault geometry plays a significant role in controlling rupture propagation and termination. The geometric barrier east of the epicenter effectively limited eastward rupture propagation, while a wide fault step near the Yushanguxi River constrained the western rupture. The Wushi earthquake was identified as a blind rupture event, with no significant primary surface rupture. The distribution of secondary geological hazards aligned well with fault slip characteristics, and the spatial relationship between aftershock slip and the mainshock highlights fault segmentation within the Ush thrust belt.

Key words: Wushi earthquake, InSAR coseismic deformation field, fault geometric parameters, sliding distribution

摘要：

文中利用Sentinel-1升、 降轨影像获取2024年乌什 M_W7.0 地震的视线向同震形变场, 并约束发震断层几何参数和滑动分布。最佳断层模型为沿走向弯折的双断层结构, 弯折前后走向变化约为25°, 倾角约有20°的差异。断层滑动为高倾角逆冲兼左旋走滑, 主要分布于震中及其西侧, 东侧幅度低且相对弥散, 整体分布具有浅部滑移亏损特征。几何差异和滑动分布的空间相关性表明发震构造在震中以东存在几何复杂体, 以障碍体模式阻碍破裂传播。同震扩展围限于玉山古溪和乌什凹陷之间, 东、 西两侧的断裂阶区和复杂构造限定了破裂规模。M_W5.7余震形成了清晰的LOS向变形, 最优模型显示其发震断层偏离主震迹线约10°, 倾向SE, 断层面地表迹线与地表破裂几乎重合, 浅层滑动量与调查所得的错断量相当。

关键词: 乌什地震, InSAR同震形变, 断层几何参数, 滑动分布