Collaborative Research: Variation of Incoming Plate Hydration and Faulting Along the Alaska Subduction Zone

合作研究：阿拉斯加俯冲带沿线板块水合作用和断层作用的变化

• 批准号: 2025969
• 负责人: Douglas Wiens
• 金额: $ 19.52万
• 依托单位: Washington University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2025969&HistoricalAwards=false
• 关键词: Collaborative; Research; Variation; Incoming; Plate

Subduction zones are sites of important chemical exchanges between the solid earth, hydrosphere and atmosphere. Seawater that penetrates into the subducting oceanic plate is incorporated in water-bearing minerals and carried deep into the earth. As the subducting plate descends and heats up, water is released and can influence the properties of subduction zone faults, the generation of subduction zone earthquakes, and the generation of magmas that feed arc volcanoes. Some of the water is released back into the atmosphere through volcanic eruptions. A critical unknown in this cycle is the amount and distribution of water in the incoming tectonic plate. How much water is stored in the plate? To what depth in the plate does water penetrate? Does the amount of water in the plate vary along the subduction zone? If so, what controls this variation? This project will use seismic and bathymetric (seafloor-depth) data collected across the Alaska subduction zone between Kodiak Island and the Shumagin Islands to constrain the volume and distribution of water stored in the subducting oceanic plate. The results will be valuable for understanding changes in the occurrence of large earthquakes and the compositions of magmas feeding volcanoes in this part of the Alaska subduction zone. Graduate and undergraduate students will participate in data analysis and gain valuable training.The volume and distribution of water is thought to control a host of fundamental processes at subduction zones, including megathrust behavior, the generation of arc magmas, and intermediate depth earthquakes. However, the amount of water delivered into the subduction zone by the incoming oceanic plate remains controversial and poorly known, resulting in great uncertainties in Earth’s deep water budget. In addition, the along-strike variation of water input, and its influence on along-strike variations in subduction processes, are also poorly constrained. Newly acquired seismic and bathymetric data from the Alaska Amphibious Community Seismic Experiment (AACSE) will be combined with existing data off the Alaska Peninsula to characterize outer-rise faulting and possible hydration throughout the incoming oceanic lithosphere. This subduction zone is an excellent target for study because it exhibits along-strike variations in megathrust coupling and seismicity at a range of depths, and existing data suggest along-strike variations in faulting and hydration. The lateral and depth distribution of hydrous phases in the incoming crust and mantle will be determined using seismic surface wave, body wave, and active source methods, and the results will be compared with incoming plate seismicity and mapped faults from bathymetry. Seismic anisotropy will provide constraints on the distribution of hydrated minerals around fault zones. The results will provide a comprehensive estimate of the incoming-plate water budget as a function of location along the Alaska subduction zone, allowing the effects of water on other subduction processes to be quantitatively evaluated. New constraints on the incoming water budget can be used by multidisciplinary studies evaluating the influence of water on megathrust and intermediate depth seismicity characteristics, along-strike volcanic output changes, and on the global mantle water budget. Estimates of the maximum size of incoming plate normal faults will allow the possible tsunami hazards of such earthquakes to be evaluated.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

俯冲带是固体地球、水圈和大气之间重要的化学交换场所，渗入俯冲海洋板块的海水与含水矿物结合，并随着俯冲板块下降和加热而被带入地球深处。释放出来的水会影响俯冲带断层的性质、俯冲带地震的产生以及为弧火山提供水源的岩浆的产生。一些水通过火山释放回大气中。这个周期中一个关键的未知因素是流入的板块中的水量和分布情况。板块中的水量会随着深度的变化而变化吗？如果是这样，是什么控制了这种变化？该项目将使用在科迪亚克岛和舒马金群岛之间的阿拉斯加俯冲带收集的地震和测深（海底深度）数据来限制俯冲带中储存的水量和分布。研究结果对于了解大地震发生的变化以及阿拉斯加俯冲带这部分火山的岩浆成分将具有重要意义。研究生和本科生将参与数据分析并获得宝贵的培训。水的分布和分布被认为控制着俯冲带的一系列基本过程，包括巨型逆冲行为、弧岩浆的产生和中深度地震。然而，传入的海洋板块输送到俯冲带的水量仍然存在争议。并且很差劲已知，导致地球深水收支存在很大的不确定性。此外，从阿拉斯加获取的地震和测深数据也很难约束水输入的沿走向变化及其对俯冲过程沿走向变化的影响。两栖社区地震实验（AACSE）将与阿拉斯加半岛附近的现有数据相结合，以表征整个传入海洋岩石圈的外隆断层和可能的水合作用。该俯冲带是一个极好的研究目标。因为它在一定深度范围内表现出巨型逆冲耦合和地震活动的沿走向变化，并且现有数据表明断层和水化作用的沿走向变化将利用地震来确定传入的地壳和地幔中含水相的横向和深度分布。表面波、体波和主动源方法，其结果将与传入的板块地震活动进行比较，并且测深绘制的断层将提供对地震分布的约束。研究结果将提供对沿阿拉斯加俯冲带位置的流入板块水收支的全面估计，从而定量评估水对其他俯冲过程的影响。水收支可用于多学科研究，评估水对巨型逆冲断层和中深度地震活动特征、沿走向火山输出变化以及对全球地幔水收支的影响，以及对传入板块法线最大尺寸的估计。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。