Earthquake Geology Along the Himalayan Frontal Thrust of India: Insight to Mechanics Earthquakes Along a Continental Convergent Plate Boundary

印度-欧亚板块边界是世界上大陆会聚的典型例子。印度和欧亚大陆之间的持续融合导致了地球上最高的山脉和有记录以来最大的陆内地震。这些事件中最大的一次发生在喜马拉雅前缘冲断带上。喜马拉雅山前冲断带沿2500公里长的喜马拉雅弧线连续延伸。喜马拉雅前缘冲断带沿走向表现为相对较短且不连续的前缘陡坎，切割晚更新世和全新世河流阶地和冲积扇。该项目是与印度瓦迪亚研究所的科学家合作进行的，得到了美国国家科学基金会地球科学部和国际科学与工程办公室的支持，正在沿着喜马拉雅弧线进行实地研究，以确定印度喜马拉雅前缘逆冲断层地震破裂的时间、大小和横向范围。对沿弧长的9个地点跨喜马拉雅前缘逆冲断层的断层陡坎挖掘沟所产生的暴露进行了结构、地层学、成壤和放射性碳研究，以提供对沿喜马拉雅前缘大地震造成的地震过程和地震危害程度的力学模型的观测约束。因为整个印度-欧亚板块边界都在海平面以上，所以这里有可能定义在沿着主要会聚板块边界的整个地震中释放的累积地壳应变的空间、时间和地表特征，这种方式和细节是沿着世界海洋会聚板块边界的水下不可能实现的。拟议的研究是应用地质技术来提取印度喜马拉雅前缘逆冲断层沿线大地震的大小和发生频率的信息。喜马拉雅前缘逆冲断层是喜马拉雅山脉南缘的边界。正是这条断层上的位移产生了许多历史上有记录的最大的大陆地震，并随着时间的推移反复发生，这是喜马拉雅山脉隆起的原因。印度人口最稠密的地区现在沿着喜马拉雅前缘冲断的南缘延伸。需要了解沿线大地震的规模和发生率，以便对公众进行教育，并为政府机构提供必要的信息，以便作出审慎的规划决策，以减轻在发生此类地震时前线潜在的财务和生命损失风险。这项研究获得的信息还将为沿逆冲断层的地震过程的机制提供观测界限，这些知识随后可能被应用于北美西部和全球其他地方的地震危险分析。

The Indian-Eurasian plate boundary is the world's type example of continental convergence. The ongoing convergence between India and Eurasia has resulted in the globes's highest mountain range and the largest recorded intracontinental earthquakes on record. The largest of these events have occurred along the Himalayan frontal thrust. The Himalayan frontal thrust extends continuously along the 2500 km length of the Himalayan arc. The Himalayan frontal thrust manifests itself along strike as relatively short and discontinuous range front scarps that cut late Pleistocene and Holocene fluvial terraces and alluvial fans. This project, carried out in collaboration with scientists from the Wadia Institute in India and supported by NSF's Division of Earth Sciences and Office of International Science and Engineering, is conducting field studies along the Himalayan arc to define the timing, size, and lateral extent of earthquake ruptures along the Himalayan frontal thrust fault in India. Structural, stratigraphic, pedogenic, and radiocarbon studies of exposures resulting from the excavation of trenches across fault scarps of the Himalayan frontal thrust fault at 9 sites along the length of the arc in order to provide observational constraints on mechanical models of the earthquake process and the level of seismic hazard imposed by large earthquakes along the Himalayan front. Because the entirety of the India-Eurasia plate boundary is above sea level, the potential exists here to define the spatial, temporal, and surficial, characteristics of accumulated crustal strain that is released in earthquakes along the entirety of a major convergent plate boundary, in a manner and detail not possible along the world's oceanic convergent plate boundaries where the thrust boundary is beneath water.The proposed research is to apply geological techniques to extract information of the size and frequency of occurrence of great earthquakes along the Himalayan frontal thrust fault of India. The Himalayan frontal thrust fault bounds the southern front of the Himalaya. It is the displacements on this fault that have produced a number of the largest continental earthquakes recorded historically and through repeated occurrence through time responsible for the uplift of the Himalaya. The most densely populated regions of India now stretch along the southern edge of the Himalayan frontal thrust. Knowledge of the size and occurrence rate of great earthquakes along the thrust is required for educating the public and providing government agencies the information needed to make prudent planning decisions to mitigate the potential financial and loss-of-life risks along the front in the event of such an earthquake. The information gained by this research will also place observational bounds on the mechanics of the earthquake process along thrust faults, knowledge that may then be applied to seismic hazard analysis in western North America and elsewhere around the globe.