本文为西藏改则县、措勤县15万地质灾害详细调查项目（编号XZDK\[2019\]- 50, 51），国家自然科学基金项目（编号41571013, 42202259），西藏自治区第一次全国自然灾害综合风险普查项目(编号XZLX- BMC- 2021- 307，XZLX- BMC- 2022- 053),中央级公益性科研院所基本科研业务费项目（编号 所科研56）和中国地质调查项目（编号DD20221644）联合资助的成果。
藏北高原非常薄弱的活动断层调查研究程度和不完整的历史地震资料等，限制了对高原内部活动构造变形特征、机制以及孕震构造环境等的深入认识。通过综合地质、遥感和地震等资料对阿里北部羌塘地块内部进行详细的活动断层解译，结合沿阿鲁错地堑系南段昆楚克错地堑西侧边界正断层新发现的晚第四纪断裂活动证据和最新同震地表破裂等，对该区的活动断层几何图像及运动学特征等进行了深入分析。研究结果表明，阿里北部的西羌塘块体内部在第四纪以发育近南北向正断层系统和由北西向与北东向走滑断层构成的共轭走滑断层系统为特征，第四纪和晚第四纪活动断层都呈现出了高密度、弥散分布的特点，并可归纳为3类基本的活动构造变形样式：共轭走滑断层及其伴生正断层作用、弥散式正断层作用和剪切裂谷式正断层作用，其中大部分正断层与走滑断层主要是作为相对独立的构造类型来共同调节区域内近东西向伸展变形的，这些特征指示藏北高原内部变形更符合“连续变形模式”而非“刚性块体挤出模式”。同时发现，沿昆楚克错地堑西缘主边界正断层发育的最新地表破裂总长度仅约400 m，最大垂直位移约0. 8 m，推测可能是1955年革吉县纳屋错东MW6. 5强震事件的结果。基于新的研究结果，推断阿鲁错地堑的第四纪正断层作用及相对频繁的历史强震活动，可能是孕育2016年阿鲁冰崩灾害的关键内动力条件，这警示需重视高原腹地活动断层作用与冰川失稳灾害之间的内在成因联系。
The poor investigation of active faults and incomplete data of historical earthquakes in the northern Tibetan Plateau limit the deep understanding to the internal active tectonic deformation mechanism and the characteristics of strong earthquakes. The active faults around northern Ngari area are interpreted in detail by integrated geological, seismic and remote sensing data, and the latest coseismic surface rupture been discovered by field surveying along the west boundary normal fault of the Kunchuke Co graben which is located in the southern segment of the Aru Co graben system. An in- depth analysis was carried out about the geometric images and kinematic characteristics of active faults around northern Ngari area, magnitude and formation time of surface rupture of Kunchuke Co based on new data. The results show that the active faults with high density and dispersive distribution are developed in the western Qiangtang block of northern Ngari area during the Quaternary period, which are dominated by the nearly south- north trending normal fault system and the conjugate strike- slip fault system composed of the NW and NE trending faults.The active tectonic deformation can be classified into three basic styles: conjugate strike- slip faulting and its associated normal faults, local diffuse normal faulting and normal faulting resulted from local rifting with shear component in western Qiangtang block. Most of normal faults do not have direct kinematic relationship with strike- slip faults, and they are mainly relatively independent active structures that jointly regulate the near east- west extensional deformation in western Qiangtang block. These characteristics indicate that the internal deformation of the central Tibetan Plateau is more consistent with the “Continuous deformation model” and not with the “rigid block extrusion model”. The latest surface rupture along the main boundary fault at the western edge of Kunchuke Co graben a typical normal fault rupture, with the surface length of nearly 400 m and the maximum vertical displacement of about 0.8 m, and maybe a small- scale surface rupture event caused by the MW 6.5 strong earthquake at east of Nawo Co in Gêgyai County in 1955. In addition, the Quaternary faulting and relatively frequent historical earthquake activity of Aru graben maybe key dynamic conditions to the 2016 giant twin glacier collapses. We suggest that the similar glacier collapses disaster risk should be taken seriously when important engineering or construction of infrastructure and urban planning are carried out around the Quaternary normal faults in central and southern Tibet.
Wu Zhonghai, Zhang Xudong, Han Shuai, Shi Yaran, Gao Yang, Ye Qiang, Nima Ciren.2022. Quaternary faulting and deformation mechanism of the western Qiangtang block in northern Ngari, Tibet[J]. Acta Geologica Sinica,96(11):3760-3783.