Collaborative Research: the role of fluids in intermediate-depth seismicity and wedge anisotropy: Case studies for Cascadia and Alaska, with a comparison to Japan

合作研究：流体在中深度地震活动和楔形各向异性中的作用：卡斯卡迪亚和阿拉斯加的案例研究，并与日本进行比较

• 批准号: 1249353
• 负责人: Peter van Keken
• 金额: $ 17.69万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-04-01 至 2017-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1249353&HistoricalAwards=false
• 关键词: Collaborative; Research; role; fluids; intermediate

The main goal of this study is to determine whether the presence of fluids within Earth's mantle is a controlling factor determining where earthquakes occur within subduction zones, specifically along the fault that enables the down-going tectonic plate to slip deeper into surrounding viscous mantle. The fact that this seismicity is located within the crust at 'cool' subduction zones, such as Alaska and Tohoku, versus in the mantle at 'warm' subduction zones, such as Cascadia and Nankai, suggests that fluids play an important role. Directional dependence of seismic wave propagation speeds will be assessed, so that possible bias in earthquake locations can be accounted for. Simultaneously, information about deformation within the viscously flowing mantle will be obtained. Ratios of shear and compressional wave velocities will suggest where fluids are present or not. These constraints will guide computer modeling of mantle flow and temperature in the subduction zones. These results will be linked to petrologic models of mineral phase change associated with plate dehydration that introduce fluids near the plate interface and lead to the generation of arc volcanism.In-depth collaboration by three geoscientists- a geodynamist, petrologist, and seismologist, serves as a model of interdisciplinary Earth System research. Graduate and undergraduate students will receive training in the use of state-of-the-art methods in their sub-discipline as well as learning how to address interplay with evolving results from complementary sub disciplines. The international collaboration with Japanese scientists provides access to the best instrumented and well-studied Japanese subduction system. The study leverages ongoing work in the NSF GeoPRISMS and EarthScope Programs at Cascadia and that planned for Alaska.

这项研究的主要目标是确定地幔内流体的存在是否是决定俯冲带内地震发生位置的控制因素，特别是沿着使下行构造板块滑入周围粘性地幔更深的断层。事实上，这种地震活动位于“冷”俯冲带（例如阿拉斯加和东北）的地壳内，而位于“暖”俯冲带（例如卡斯卡迪亚和南海）的地幔中，这一事实表明流体发挥着重要作用。将评估地震波传播速度的方向依赖性，以便可以考虑地震位置可能存在的偏差。同时，还将获得有关粘性流动地幔内变形的信息。剪切波和压缩波速度的比率将表明哪里存在或不存在流体。这些约束将指导俯冲带地幔流和温度的计算机建模。这些结果将与与板块脱水相关的矿物相变岩石学模型联系起来，板块脱水在板块界面附近引入流体并导致弧火山活动的产生。三位地球科学家（地球动力学家、岩石学家和地震学家）的深入合作，作为跨学科地球系统研究的模型。 研究生和本科生将接受在其子学科中使用最先进方法的培训，并学习如何解决与互补子学科不断发展的结果的相互作用。与日本科学家的国际合作提供了使用最好的仪器和经过充分研究的日本俯冲系统的机会。该研究利用了 NSF GeoPRISMS 和 EarthScope 计划在卡斯卡迪亚以及计划在阿拉斯加开展的工作。