Abstract As occurred during the tourist season, the 2017 Mw 6.5 Jiuzhaigou (China) earthquake led to destructive damages. The seismogenic fault of this event was merely speculated to be the northern extension of the Huya fault, while no apparent surface ruptures were discovered in the field investigation. Previous studies and released moment tensor solutions indicated the Jiuzhaigou earthquake was dominated by left-lateral strike slip with partial normal-slip component. It seems unintelligible that the normal slip occurred in this event as the epicenter was located near the boundary of convergent blocks. Hence, a reasonable and elaborate source rupture model is necessary to investigate such a blind fault and the role it plays in the complex fault system of this region. Combining space-based geodetic, teleseismic or regional seismic observations can provide detailed information about earthquake ruptures. We first attempted to determine the fault geometry using the Bayesian approach with synthetic aperture radar interferograms (InSAR). And then the fault geometry was refined based on the relocated aftershock distribution, and a two-segment fault model was constructed. Based on the two-segment model, we resolved the source rupture process of the 2017 Jiuzhaigou earthquake through the joint inversion of strong-motion, teleseismic body-wave and InSAR data. The inversion results reveal a hybrid source mechanism, in which normal and thrust slips coexist besides the strike-slip component. We suggest that the eastward motion with the extrusion of the lower crustal flow in the northeastern margin of the Bayan Har block is responsible for such a faulting behavior. The co-seismic Coulomb stress changes show a significant stress loading in the western segment of the Tazang fault, increasing its seismic hazard. Due to the lack of aftershocks to the southeast of the seismogenic fault, the probably enhanced seismicity in the northern segment of the Huya fault is also worth further attention.

中文翻译：

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强震、远震和InSAR数据联合反演揭示2017年6.5级九寨沟地震混合震源机制

摘要 2017 年发生在旅游旺季的 6.5 级九寨沟地震造成了破坏性破坏。此次事件的发震断层仅推测为虎牙断裂的北延，现场调查未发现明显的地表破裂。以往的研究和释放的矩张量解表明，九寨沟地震以左旋走滑为主，部分为法向滑移。由于震中位于会聚块的边界附近，因此在此事件中发生正常滑动似乎令人费解。因此，需要一个合理、精细的震源破裂模型来研究这种盲断层及其在该地区复杂断层系统中的作用。结合天基大地测量，远震或区域地震观测可以提供关于地震破裂的详细信息。我们首先尝试使用贝叶斯方法和合成孔径雷达干涉图 (InSAR) 来确定断层几何形状。然后根据重定位余震分布细化断层几何结构，构建两段断层模型。基于二段模型，我们通过强震、远震体波和InSAR数据的联合反演，解析了2017年九寨沟地震震源破裂过程。反演结果揭示了一种混合源机制，其中除了走滑分量外，法向滑移和逆冲滑移共存。我们认为，巴颜喀拉地块东北缘下地壳流挤压向东运动是造成这种断层行为的原因。同震库仑应力变化表明塔藏断层西段有显着的应力载荷，增加了其地震危险性。由于发震断裂东南部没有余震，虎牙断裂北段地震活动可能增强也值得进一步关注。