Mechanics of Earthquake Faulting along the Himalayan Convergent Plate Boundary

这个研究项目有几个要素。首先，这项研究旨在定义印度喜马拉雅前缘冲断带(HFT)过去大地震的历史，从而确定应变释放。在这里，地质原理被用来确定世界上最大的大陆逆冲断层上过去大地震的大小、发生频率和位置。之所以选择研究地点，是因为印度提供了独特的情况，与反复发生的地震有关的整个地壳变形都位于陆地上。这项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程度与大地测量测量的应变累积的持续测量之间的关系。了解了这种关系，就有可能使用正在进行的大地应变测量来预测未来主要活动断裂带上未来大地震的大小和位置，不仅在印度，而且在其他主要断裂带沿线，如贯穿美国的圣安德烈亚斯。其次，与印度调查人员的国际合作有一个协同因素，它将利用NSF的资金收集比单独使用NSF资金可能收集到的更多的观察数据。第三个要素是教育，包括培训几名博士生，让本科生参与一个激动人心的国际项目，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，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，向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和构造学短期课程。因此，拟议的项目将为未来新兴青年科学家之间的国际合作产生独特的联系。它将直接影响对地震危险性的评估，并提高对这一世界上人口最稠密的巨型逆冲断层沿线的地震风险的认识，特别是对那些旨在减轻和应对自然灾害的机构。这项研究所采用的方法将需要绘制印度喜马拉雅前缘冲断带(HFT)沿线被地震抵消的第四纪沉积物和地表的地图和年代。由高频傅里叶变换绘制的第四纪表面的年龄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定义每个研究地点数千年来平均的喜马拉雅前缘冲断(HFT)偏移率。地图还将用于定义最适合在高频交易中布设战壕的地点。海沟中暴露的构造、沉积学和地层关系将是确定取代矿藏的地震的数量、规模和时间的基础。该项目的目标是在大约2500公里长的高频傅里叶变换沿线多达9个地点实施该方法。这些观测结果与先前研究的结果相结合，将为评估先前大地震沿高频傅里叶变换长度的破裂长度和同震滑移量提供依据。最终，通过收集这类数据并将其与应变累积的地球物理测量进行比较，地震界将增进对控制未来地震规模的物理因素的了解。

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.