Investigation of the hydrogeologic role of faults in the downgoing plate through comparison of Central America, Cascadia, Nankai, and Alaska subduction zones

通过比较中美洲、卡斯卡迪亚、南开和阿拉斯加俯冲带研究下降板块中断层的水文地质作用

• 批准号: 1457221
• 负责人: Nathan Bangs
• 金额: $ 25.7万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-04-01 至 2018-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1457221&HistoricalAwards=false
• 关键词: Investigation; hydrogeologic; role; faults; downgoing

Part 1The award will fund a GeoPRISMS postdoctoral Fellowship for two years of training at the University of Texas, Institute for Geophysics (UTIG). The proposed work seeks to quantitatively determine the structure and water content in the faults within the select segments of the subducting plates. This will allow the assessment of the effects of subducting water on subduction zone processes. The study will use existing 2D and 3D multichannel seismic data from Central America, Cascadia, Nankai, and Alaska subduction zones. The results will provide a better understanding of the geohazard potential in subduction zones, which is particularly relevant for the Pacific Northwest region where large magnitude earthquakes have occurred on the Cascadia megathrust in recent history. The postdoctoral fellow is an early-career female scientist. The results of the study will be presented at workshops and conferences and will contribute to the high school curriculum development program at UTIG. Part 2Funds are provided for a postdoctoral fellow to conduct amplitude preserved seismic prestack depth migration, 2D waveform modeling of fault plane reflections, and fluid flow modeling of the 2D multichannel seismic data at Nicaragua, Cascadia, Nankai, and Alaska subduction zones to explore the limits on the water content of the fault zones in the oceanic plate seaward of the trench. From these results she will begin to quantitatively assess the hydration state of incoming plate at different subduction zones. The seismic attribute analysis of decollement, near-basement sediment, and basement crustal rocks, and the waveform modeling of the faults in the down-going plate beneath the slope in Nankai and Costa Rica 3D datasets will allow the assessment of fluid exchange between the hydrologic systems of upper and lower plate. The post-doctoral fellow will identify water expulsion along faults in the down- going plate as it migrates upward into the upper plate. The results from this study will contribute to answer the two key questions in the GeoPRISMS Subduction Cycles and Deformation science plan: "How are volatiles, fluids, and melts stored, transferred, and released through the subduction system?" and "How do volatile release and transfer affect the rheology and dynamics of the plate interface, from the incoming plate and trench through to the arc and backarc?"Broader Impacts: The proposed work will provide a better understanding of the geohazard potential in subduction zones, which is particularly relevant for the Pacific Northwest region where large magnitude earthquakes have occurred on the Cascadia megathrust in recent history. The project will support the postdoctoral training of an early-career female scientist. The results of the study will be presented at workshops and conferences and will contribute to the high school curriculum development program at UTIG.

该奖项将资助在德克萨斯大学地球物理研究所(UTIG)进行为期两年的培训的GeoPRISMS博士后奖学金。这项拟议的工作旨在定量确定俯冲板块选定区段内断层的结构和含水率。这将使评估水俯冲对俯冲带过程的影响成为可能。这项研究将使用来自中美洲、卡斯卡迪亚、南开和阿拉斯加俯冲带的现有2D和3D多道地震数据。这一结果将有助于更好地了解俯冲带的地质灾害潜力，这对于近年来卡斯卡迪亚巨型逆冲带上曾发生过大震级地震的太平洋西北部地区尤为重要。博士后研究员是一位职业生涯早期的女科学家。研究结果将在研讨会和会议上公布，并将为UTIG的高中课程开发计划做出贡献。第二部分为博士后人员提供了在尼加拉瓜、卡斯卡迪亚、南开和阿拉斯加俯冲带进行保幅地震叠前深度偏移、断层面反射的二维波形模拟和二维多道地震数据的流体流动模拟的基础，以探索海沟洋板向海的断裂带的含水率极限。根据这些结果，她将开始定量评估不同俯冲带上来的板块的水化状态。在南开和哥斯达黎加三维数据集上，对滑脱、近基底沉积和基底地壳岩石进行地震属性分析，并对斜坡下方的下行板块中的断层进行波形模拟，将可以评估上下板块水文系统之间的流体交换。这位博士后研究员将在下沉板块向上迁移到上板块的过程中识别沿着断层排出的水。这项研究的结果将有助于回答GeoPRISMS俯冲旋回和形变科学计划中的两个关键问题：挥发物、流体和熔体是如何通过俯冲系统储存、转移和释放的？和“挥发分的释放和转移如何影响板块界面的流变性和动力学，从进入的板块和海沟到弧形和弧后？”更广泛的影响：拟议的工作将提供更好的了解俯冲带的地质灾害潜力，这与太平洋西北部地区特别相关，该地区近年来在卡斯卡迪亚巨型逆冲上发生过大震级地震。该项目将支持对一名职业生涯早期的女科学家进行博士后培训。研究结果将在研讨会和会议上公布，并将为UTIG的高中课程开发计划做出贡献。