藏北高原近南北向地堑群晚新生代正断层活动的时空特性与规律研究

围绕藏北高原近南北向地堑群的时空发育特征、成因机制及其与高原隆升关系这一关键科学问题。本项目拟以其中典型的安多地堑群为重点研究对象，针对地堑主边界正断层的几何学、运动学特征及第四纪活动的时空特性等内容，综合应用高精度遥感解译、基于数字高程的构造地貌分析、地表活动断裂调查、断层崖高度测量和低温热年代学等多种方法，并结合14C、OSL、U 系、ESR、FT和U-Th-He等年代学测试分析手段，定量约束近南北向地堑及其边界正断层的演化过程与百万至万年不同时间尺度的活动习性，从多角度和多时空尺度揭示该区晚新生代正断层作用的时空差异性、变化特征及规律。同时结合已有研究，开展与藏南近南北向正断层的对比分析，进而系统总结高原内部正断层作用的时空特征与规律，深入剖析其成因机制，提升对青藏高原正断层作用动力学机制及其与高原隆升关系的认识，并增进对活动造山带中板内裂谷作用特性的理解。

The diffuse graben groups in central-northern Tibet and normal faulting along the south-north trending rift systems in southern Tibet are dominant active tectonic character in Qinghai-Xizang Plateau. The characteristics and dynamic mechanism of normal faulting are very important focus on understanding the timing and manner of the Qinghai-Xizang Plateau uplift. But many evidences for the models of extension across the Tibetan Plateau during late Cenozoic or Quaternary have been from studies on active north-south trending normal faults in southern Tibet, only seldom researches have related to active normal faulting in central Tibet. So, it is clearly, more data on the spatial and temporal distribution of normal faulting across the Tibetan Plateau, particularly within the central Tibet, are needed to understand the causes of EW extension across Tibet and constrain the relation with uplift of Tibet. Based on previous studies on active normal faulting in central Tibet, in this research project, we select the Amdo graben group which activity and scale are very prominent in the central-northern Tibet as the main study area. We will mainly study the geometric and kinematic characteristic, Quaternary activity, typical paleo-earthquake events and their ages, especial to unitize the multi-generation fault scarps which are formed by normal fault offset late Quaternary (about since 250ka before present) various geomorphic units to study late Quaternary normal faulting along the Amdo graben system. In the study, the vertical slip rate of normal faults in various time-scale including millenary, 10ka, 100ka and 1Ma, will be obtained by field surveying, tectonic geomorphology and Digital elevation model across grabens analysis, detailed fault scarps measuring and late Quaternary deposits dating using various chronological techniques including carbon-14, OSL, U-series, ESR, Fission track and U-Th-He so on. Because the various time-scale slip rates of normal faults will reveal the temporal and spatial active character of the main boundary normal faults along Amdo graben group, and constrain the kinematic and dynamic mechanism on extension deformation of the central-northern Tibet graben systems. Father, studying the multiple time-scale slip rates of normal faulting along the Amdo graben group also is an important approach to understand the behavior of normal faulting of intraplate rift system, the law of large earthquake migration along the south-north trending graben system and active characteristic of rift system in active collision orogenic belt between Indie and Eurasia plate. Finally, the comparative study on S-N trending normal faulting between southern and central in Tibet will be carry out to understand and constrain the causes of east-west extension deformation across Tibet during Quaternary and relationship with uplift of Tibet Plateau.