Mechanics of Earthquake Faulting along the Himalayan Convergent Plate Boundary

这个研究项目有几个要素。首先，有一项研究旨在确定大地震的过去历史，从而沿着印度喜马拉雅前缘冲断层（HFT）释放应变。 在这里，地质学原理被用来确定过去的规模，发生频率和大地震位移的位置沿着世界上最大的大陆逆冲断层。选择研究地点是因为印度提供了独特的情况，与经常发生的地震有关的地壳变形全部位于陆地上。研究的最终目的是比较和了解地质学中观测到的地震位移的大小和范围与大地测量学测量的应变积累的持续测量之间的关系。了解这种关系，就有可能持续测量大地应变，用于预测未来大地震的规模和位置，这些大地震不仅发生在印度，也发生在其他沿着其他主要断层带的沿着，如贯穿美国的圣安德烈亚斯。第二，与印度调查人员的国际合作具有协同作用，这将利用NSF的资金收集比单独使用NSF资金可能更多的观测结果。第三个要素是教育，包括培养几个博士。该项目的主要成果包括：在意大利的里雅斯特国际理论物理中心的后勤和财政援助下，邀请学生参与一个令人兴奋的国际项目，解决断层力学中的一个基本问题，并利用拟议的研究作为平台，为来自印度和周边发展中国家的学生和科学家开设喜马拉雅山脉物理学和构造学短期课程。 因此，拟议的项目还将为新兴青年科学家之间未来的国际合作建立独特的联系。它将直接影响地震危险性评估，并提高人们对世界上人口最稠密的巨型逆冲断层沿着地震风险的认识，特别是那些旨在减轻和应对自然灾害的机构。这项研究中采用的方法将需要绘制和测年印度喜马拉雅正面逆冲断层（HFT）沿着地震所抵消的第四纪沉积物和表面。第四纪表面的年龄将由HFT绘制的偏移将通过从矿床中提取的木炭样品的放射性碳分析来确定。将偏移量除以沉积物的年龄将确定喜马拉雅锋面逆冲断层（HFT）偏移量的速率，该速率在所研究的每个地点经过数千年的平均值。测绘还将用于确定最适合在HFT上放置战壕的地点。海沟中暴露的结构、沉积学和地层关系将是确定使矿床移位的地震的数量、规模和时间的基础。 本项目的目标是在沿~2500 km长的HFT沿着的9个站点实施该方法。 由此产生的观测结果，当与先前的研究结果相结合时，将提供基础来评估破裂长度和沿着HFT长度的先前大地震的同震滑动量。最终，通过收集这类数据并将其与应变积累的地球物理措施进行比较，地震学界将进一步了解控制未来地震规模的物理因素。

There are several elements to this research project. First, there is the research directed to define the past history of great earthquakes and thus strain release along the Himalayan Frontal Thrust (HFT) of India. Here geological principals are used to determine the past size, frequency of occurrence, and location of great earthquake displacements along the greatest continental thrust fault in the world. The location of the study is chosen because India affords the unique situation where the entirety of the crustal deformation associated with recurring earthquakes is situated on land. The ultimate purpose of the study is to compare and understand the relationship of the size and extent of earthquake displacements observed in the geology to ongoing measures of strain accumulation measured by geodesy. Understanding this relationship holds the potential for ongoing measures of geodetic strain to be used to predict the size and location of future great earthquakes along major active fault zones not just in India but also elsewhere along other major fault zones such as the San Andreas which runs through the United States. Second, there is a synergistic element of international cooperation with Indian Investigators that will leverage funding from NSF to collect many more observations than would likely be possible with funding from NSF alone. The third element is education, including the training of several Ph.D. students, the involvement of undergraduates in an exciting international project addressing a fundamental problem in fault mechanics, and the use of the proposed research as a platform to conduct a short course in Himalayan geophysics and tectonics to students and scientists from India and surrounding developing nations with the logistical and financial assistance of the International Centre for Theoretical Physics of Trieste, Italy. Thus, the proposed project will additionally produce unique liaisons for future international collaboration between emerging young scientists. It will directly impact assessment of seismic hazard and raise awareness of seismic risk along this most densely populated megathrust fault in the world, particularly for those in agencies aimed at mitigating and responding to natural disasters.The methodology employed in this research will entail the mapping and dating of Quaternary deposits and surfaces that have been offset by earthquakes along the Himalayan Frontal Thrust of India (HFT). The age of Quaternary surfaces mapped to be offset by the HFT will be determined with radiocarbon analysis of charcoal samples taken from the deposits. Dividing the amount of the offset by the age of the deposits will define the rate of Himalayan Frontal Thrust (HFT) offset averaged over thousands of years at each site studied. The mapping will also serve to define sites that are most amenable to placing trenches across the HFT. Structural, sedimentological, and stratigraphic relationships exposed in the trenches will be the basis to determine the number, size and timing of earthquakes that have displaced the deposits. It is the goal of this project to implement the methodology at up to 9 sites along the ~2500 km length of the HFT. The resulting observations will, when combined with the results of prior studies, provide the basis to assess the rupture length and amount of coseismic slip of prior great earthquakes along the length of the HFT. It is ultimately through the collection of this type of data and its comparison to geophysical measures of strain accumulation that the seismological community will advance understanding of the physical factors that control the size of future earthquakes.