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，从而确定印度喜马拉雅锋面逆冲（HFT）沿线的应变释放。在这里，地质学原理被用来确定世界上最大的大陆逆冲断层沿线大地震过去的规模、发生频率和位置。之所以选择研究地点，是因为印度具有独特的条件，与反复发生的地震相关的地壳变形全部位于陆地上。这项研究的最终目的是比较和理解在地质学中观察到的地震位移的大小和程度与正在进行的测量测量的应变积累之间的关系。了解了这种关系，就有可能利用测量大地应变的方法来预测未来大地震的大小和位置，这些地震不仅发生在印度，也发生在其他地方的主要断裂带，比如贯穿美国的圣安德烈亚斯断层。其次，与印度研究人员的国际合作具有协同作用，这将利用国家科学基金会的资金来收集比单独由国家科学基金会提供资金可能收集到的更多的观察结果。第三个要素是教育，包括培养几名博士生，让本科生参与解决故障力学基本问题的令人兴奋的国际项目，并利用拟议的研究作为平台，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，为来自印度和周边发展中国家的学生和科学家举办喜马拉雅地球物理学和构造学的短期课程。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提供独特的联系。它将直接影响地震危险的评估，并提高人们对这个世界上人口最密集的大逆冲断层沿线地震风险的认识，特别是那些旨在减轻和应对自然灾害的机构。本研究中采用的方法将需要绘制第四纪沉积物和地表的地图并确定年代，这些沉积物和地表已被印度喜马拉雅锋面逆冲（HFT）沿线的地震所抵消。第四纪地表的年龄将通过对从沉积物中提取的木炭样品进行放射性碳分析来确定。将偏移量除以沉积物年龄将确定喜马拉雅锋面逆冲（HFT）偏移在每个研究地点数千年的平均速率。该地图还将用于确定最适合在高频交易中放置战壕的地点。在海沟中发现的构造、沉积学和地层关系将是确定使沉积物移位的地震的次数、大小和时间的基础。该项目的目标是在高频交易2500公里长的9个地点实施该方法。所得的观测结果与先前的研究结果相结合，将为评估沿高频高频带长度的先前大地震的破裂长度和同震滑动量提供基础。最终，通过收集这类数据并将其与应变积累的地球物理测量进行比较，地震学界将增进对控制未来地震大小的物理因素的理解。

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.