The present east–west crustal extension of the Tibetan Plateau has been demonstrated through field investigations, satellite imagery, geodetic deformation, and earthquake focal mechanisms. Normal faulting earthquakes in the interior Tibetan Plateau are almost entirely confined to regions at elevations over 4000 m. However, our knowledge of the eastward extent of normal faulting in the plateau is still uncertain due to the limited occurrence of well-documented earthquakes. Based on a retrospective analysis of the 2016 Mw 5.9 Zaduo earthquake in the Tibetan Plateau, we consider the NE trending Zaduo-Shanglaxiu fault as the most likely rupture fault through a comprehensive analysis of relocated aftershock sequences, mapped active faults, and newly acquired strain rate tensor. We further determine seismogenic fault geometry using a Bayesian approach and sample with a Markov Chain Monte Carlo method. We interpret the Zaduo earthquake to reflect the release of slowly accumulated elastic strain accumulated mainly by gravitational forces rather than a delay triggering event from the 2010 Yushu earthquake. The viscoelastic calculations to estimate Coulomb stress changes over time indicate that long-term viscous flow in a weak mid-crust can load adjacent faults far more than static stress changes alone. Our results show that the Zaduo earthquake was a Mw 5.9 oblique normal faulting event that occurred in the easternmost part of the Tibetan Plateau, suggesting that the Qiangtang block at longitude ~ 95° E accommodates east–west extensional crustal deformation by small-scale oblique normal faults, which may act as the boundary of micro-blocks. This may also mean that the normal faulting in the Qiangtang block is expanding outwards, and a new rifting system may be formed, which requires more geological evidence.

中文翻译：

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2016年扎多5.9级地震期间的斜断层运动：对青藏高原Qian塘地块区域构造的认识

通过实地调查，卫星图像，大地变形和地震震源机制已经证明了青藏高原目前东西向的地壳扩展。青藏高原内部的正常断层地震几乎完全局限于海拔4000 m以上的区域。然而，由于有据可查的地震有限，我们对高原正断层向东延伸的认识仍不确定。通过对2016年青藏高原扎多5.9级地震的回顾性分析，通过对重新定位的余震序列，测绘的活动断层和新获得的应变率进行综合分析，我们认为NE趋势的扎多-上拉秀断层是最有可能破裂的断层张量。我们进一步使用贝叶斯方法确定震源断层的几何形状，并使用马尔可夫链蒙特卡罗方法进行采样。我们将Zaduo地震解释为反映了主要由重力积累的缓慢累积的弹性应变的释放，而不是2010年玉树地震的延迟触发事件。估计库仑应力随时间变化的粘弹性计算表明，在弱地壳中的长期粘性流对相邻断层的负荷远大于单独的静态应力变化。我们的结果表明，扎多地震是发生在青藏高原最东部的5.9 Mw斜向正断层事件，表明经度〜95°E的Qian塘地块可适应小规模斜向正西向东西向伸展的地壳变形缺点 可以作为微块的边界。这也可能意味着the塘区块的正断层正在向外扩展，并可能形成新的裂谷系统，这需要更多的地质证据。