Investigating the Slip Rate of the Main Frontal Thrust in the Eastern Himalaya, NE India

长2500公里的喜马拉雅主锋冲断层是世界上最长的活动逆冲断层。它通过印度次大陆东西两侧的活动左滑和右滑转换压系统将大洋俯冲带连接起来。这些活动断裂共同适应了印度板块向北压入欧亚板块的持续变形，这种变形促进了喜马拉雅山带目前的增长。尽管主锋推力可能吸收了喜马拉雅中部目前印度-亚洲汇聚总量的50%以上，但它的滑移率如何随着走向而变化仍然鲜为人知。例如，主锋推力滑移率是否从西向东增加，是否与印度-亚洲收敛速度向东增加相对应，目前尚不清楚。解决这一问题是确定喜马拉雅组动力成因的关键。确定主锋冲断层滑移率分布的一个主要困难是缺乏关于喜马拉雅东部主锋冲断层的地质信息。这个由NSF资助的项目正在通过进行详细的结构、形态和地质年代学调查来解决这个问题。该项目的最终成果包括(1)对喜马拉雅东部主要前缘逆冲的第四纪滑动速率的可靠估计，以及(2)喜马拉雅东部第一张详细的活动断层图。这一研究项目将有助于对1897年发生在锡隆高原北缘的阿萨姆邦8.6级地震和1950年在喜马拉雅东端发生的8.5级梅托格地震的印度东北部进行地震危险性评估。我们关于喜马拉雅东部活动构造分布和活动断裂速率的最终报告将提交给印度地方和中部政府。除了这项研究的科学目标外，该项目还支持加州大学洛杉矶分校一名美国研究生的培训和研究工作，以及与印度研究人员和研究生的合作。该项目得到了EAR构造计划和OISE全球风险基金的支持。

The 2500-kilometer-long Himalayan Main Frontal Thrust is the longest active thrust fault in the world. It links the oceanic subduction zones via active left-slip and right-slip transpressional systems on the east and west sides of the Indian subcontinent. Together, these active faults accommodate on-going northward indentation of the Indian plate into the Eurasian plate and this deformation contributes to the current growth of the Himalayan mountain belt. Although the Main Frontal Thrust may have absorbed more than 50% of the total current India-Asian convergence in the central Himalaya, how its slip rate varies along strike remains poorly known. For example, it is not clearly if the Main Frontal Thrust slip rate increases from west to east corresponding to the eastward increase in the rate of India-Asia convergence. Resolving this problem is a key to establishing the dynamic cause of the Himalayan formation. A major difficulty in determining the slip-rate distribution of the Main Frontal Thrust is the lack of geologic information on the Main Frontal Thrust in the eastern Himalaya. This NSF-funded project is addressing this issue by conducting detailed structural, morphologic, and geochronologic investigations. The final products of the project include (1) a robust estimate of the Quaternary slip rate on the Main Frontal Thrust in the eastern Himalaya, and (2) a first detailed active-fault map of the eastern Himalaya. This research project will benefit seismic-hazard evaluation of NE India that hosted the devastating 1897 M = 8.6 Assam earthquake along the northern edge of the Shillong Plateau and 1950 M = 8.5 Metog earthquake at the eastern end of the Himalaya. The final report of our findings on the distribution of active structures and the rates of active faults in the eastern Himalaya will be submitted to the local and central Indian governments. In addition to the scientific objectives of this study, the project is supporting the training and research efforts of a U.S. graduate student at UCLA, as well as collaboration with Indian researchers and graduate students. The project is supported by the EAR Tectonics Program and the OISE Global Venture Fund.