Mapping subduction-induced Mantle Flow Underneath North/Central America and Europe

绘制北美洲/中美洲和欧洲下方俯冲引起的地幔流图

• 批准号: 1924282
• 负责人: Hejun Zhu
• 金额: $ 15.76万
• 依托单位: University of Texas at Dallas
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1924282&HistoricalAwards=false
• 关键词: Mapping; subduction; induced; Mantle; Flow

Mapping mantle flow induced by the descending oceanic lithosphere has important implications for understanding subduction processes. Two fundamental types of subduction-induced mantle flows have been suggested based on laboratory experiments, mantle flow computer simulations and shear wave splitting measurements. However, to date, the behaviors of these flow modes at different depths in an actual subduction environment remain elusive. In this project, the PI proposes to characterize mantle flow circulation patterns for five active convergent margins in North/Central America and Europe: the Middle America, Caribbean, Cascadia, Calabria and Hellenic. Analyzing these results will improve our understanding of the thermal and chemical evolution of subduction systems. In addition, Central America, Cascadia and the Mediterranean are among the most seismologically active regions in the world. With the new 3-D tomographic models, the team will numerically simulate Earth's responses associated with a number of past and future large magnitude earthquakes in these regions, which may provide valuable information about earthquake hazards in densely populated regions. This project will advance the development of the University of Texas, Dallas Seismic Imaging Laboratory by supporting an early career PI and one Ph.D. graduate student. Results from this project will be disseminated via peer-reviewed publications and presentations at national/international meetings. With the support of this project, the PI's team will use full waveform inversion to constrain 3-D azimuthal anisotropy structures for five subduction systems in North/Central America and Europe. This inversion strategy offers a unified framework to simultaneously constrain multiple seismic parameters, and enables the team to better extract quantitative information about Earth materials by fitting recorded waveforms with full-wavefield modeling results. The PI plans to combine three-component body and surface waves to simultaneously constrain wavespeeds and azimuthal anisotropy from the crust down to the transition zone. By examining correlations between wavespeed anomalies and anisotropic fabrics, the PI wants to address the following three fundamental questions: (1) How are the poloidal- and toroidal-mode mantle flows competing and interfering with each other at different depths in the back-arc, fore-arc and sub-slab regions? (2) What are the effects of slab detachment and tearing on the circulation of mantle flows? (3) How do mantle flows respond as the slabs penetrate the 660-km discontinuity or flatten within the transition zone? Answering these questions will have implications for understanding subduction processes in different disciplines of Earth Sciences.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.

绘制由下降的海洋岩石圈引起的地幔流图对于理解俯冲过程具有重要意义。基于实验室实验、地幔流计算机模拟和剪切波分裂测量，提出了两种基本类型的俯冲引起的地幔流。然而，迄今为止，在实际俯冲环境中不同深度的这些流动模式的行为仍然难以捉摸。在该项目中，PI建议描述北美/中美洲和欧洲五个活跃辐合边缘的地幔流循环模式：中美洲、加勒比海、卡斯卡迪亚、卡拉布里亚和希腊。分析这些结果将提高我们对俯冲系统的热和化学演化的理解。此外，中美洲、卡斯卡迪亚和地中海是世界上地震最活跃的地区之一。利用新的 3D 断层扫描模型，该团队将数值模拟地球与这些地区过去和未来的多次大地震相关的响应，这可能提供有关人口稠密地区地震危害的宝贵信息。该项目将通过支持一名早期职业 PI 和一名博士来推动德克萨斯大学达拉斯分校地震成像实验室的发展。研究生。该项目的结果将通过同行评审的出版物和在国家/国际会议上的演讲进行传播。在该项目的支持下，PI团队将使用全波形反演来约束北美/中美洲和欧洲五个俯冲系统的3D方位各向异性结构。这种反演策略提供了一个统一的框架来同时约束多个地震参数，并使团队能够通过将记录的波形与全波场建模结果进行拟合来更好地提取有关地球物质的定量信息。 PI 计划将三分量体波和表面波结合起来，同时限制从地壳到过渡区的波速和方位各向异性。通过研究波速异常和各向异性结构之间的相关性，PI 希望解决以下三个基本问题：（1）极向模式和环形模式地幔流在弧后不同深度如何相互竞争和干扰，弧前和亚板区域？ （2）板片脱离和撕裂对地幔流循环有何影响？ (3) 当板片穿透 660 公里的不连续面或在过渡带内变平时，地幔流如何响应？回答这些问题将对理解地球科学不同学科的俯冲过程产生影响。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Azimuthal Anisotropy of the North American Upper Mantle Based on Full Waveform Inversion

• DOI: 10.1029/2019jb018432
• 发表时间: 2020-02
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: Hejun Zhu;Jidong Yang;Xueyan Li

Poloidal‐ and Toroidal‐Mode Mantle Flows Underneath the Cascadia Subduction Zone

卡斯卡迪亚俯冲带下方的极向模式和环形模式地幔流

• DOI: 10.1029/2020gl087530
• 发表时间: 2020
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Zhu, Hejun;Li, Xueyan;Yang, Jidong;Stern, Robert J.;Lumley, David E.
• 通讯作者: Lumley, David E.

Seismic evidence for subduction-induced mantle flows underneath Middle America

• DOI: 10.1038/s41467-020-15492-6
• 发表时间: 2020-04
• 期刊: Nature Communications
• 影响因子: 16.6
• 作者: Hejun Zhu;R. Stern;Jidong Yang