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，水圈和大气之间重要化学交换的位置。穿透到俯冲海洋板的海水被纳入水矿物中，并深入地球。随着俯冲板的下降和加热，水被释放，可以影响俯冲带断层的特性，俯冲带的产生以及供电弧火山的岩浆产生。一些水通过火山喷发释放回了大气。该周期中的关键未知是传入的构造板中水的数量和分布。盘子中存储多少水？水渗透到盘子中的深度？盘子中的水量在俯冲带上会有所不同吗？如果是这样，什么控制了这种变化？该项目将使用在Kodiak Island和Shumagin群岛之间收集的跨阿拉斯加俯冲带收集的地震和测深（海底深度）数据，以限制俯冲海洋板中存储的水的体积和分布。结果对于理解大地震发生的变化以及在阿拉斯加俯冲带的这一部分的发生变化和岩浆进食火山的组成将是有价值的。研究生和本科生将参与数据分析并获得宝贵的培训。被认为水的数量和分配可以控制俯冲区域的许多基本过程，包括巨型行为，弧形岩浆的产生以及中间深度地震。但是，通过到达的海洋板传递到俯冲带的水量仍然有争议且知名度不佳，导致地球深水预算中的不确定性极大。此外，水输入的及曲状差异及其对俯冲过程中沿撞击变化的影响也受到了很大的控制。来自阿拉斯加两栖社区地震实验（AACSE）的新获得的地震和测深数据将与阿拉斯加半岛上的现有数据相结合，以表征整个即将到来的海洋岩石圈的外层断层和可能的水合。该俯冲带是研究的绝佳目标，因为它在一系列深度范围内表现出巨型耦合和地震性的局势变化，现有数据表明断层和水合的撞击变化。将使用地震表面波，人体波和活动源方法确定传入地壳和地幔中含水相的横向和深度分布，并将结果与​​接入板的地震性和映射的故障进行比较。地震各向异性将对断层区域周围的水合矿物分布提供约束。结果将对进入板的水预算作为沿阿拉斯加俯冲带的位置的函数提供全面的估计，从而使水对其他俯冲过程的影响进行定量评估。多学科研究可以使用对进水预算的新限制，以评估水对大型和中间深度地震性特征的影响，沿着火山污染物的变化以及全球地幔水预算的影响。对传入板正常断层的最大尺寸的估计将允许评估这种地震的海啸危害。该奖项反映了NSF的法定任务，并通过使用基金会的知识分子和更广泛的影响审查标准来评估NSF的法定任务。