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.

降落的海洋岩石圈诱导的地幔流对理解俯冲过程具有重要意义。根据实验室实验，地幔流量计算机模拟和剪切波拆分测量结果，已经提出了两种基本类型的俯冲引起的地幔流。但是，迄今为止，在实际的俯冲环境中，这些流程模式在不同深度处的行为仍然难以捉摸。在该项目中，PI提议表征北美洲和欧洲五个主动收敛边缘的地幔流循环模式：中美洲，加勒比海，卡斯卡迪亚，卡拉布里亚和希腊人。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最活跃的地区之一。借助新的3D断层扫描模型，该团队将在数值上模拟与这些地区的许多过去和未来大级地震相关的地球反应，这可能会提供有关人口稠密地区地震危害的有价值信息。该项目将通过支持早期职业PI和一位博士学位来推进得克萨斯大学，达拉斯地震成像实验室的发展。研究生。该项目的结果将通过国家/国际会议上的同行评审出版物和演讲传播。在该项目的支持下，PI的团队将使用完整的波形反演来限制北美/中美洲和欧洲五个俯冲系统的3D方位角各向异性结构。这种反演策略提供了一个统一的框架来同时限制多个地震参数，并使团队通过将记录的波形与全波场建模结果拟合，使团队能够更好地提取有关地球材料的定量信息。 PI计划将三组分的身体和表面波相结合，以同时限制从外壳向下到过渡区的波动和方位角各向异性。通过检查波动异常与各向异性织物之间的相关性，PI希望解决以下三个基本问题：（1）Poloidal-和Toroidal-Mode地幔的近距离流动如何在背面，Arc，Arc，Arc-Arc和Subselabab区域的不同深度相互竞争和干预？ （2）平板脱离和撕裂对地幔流循环的影响是什么？ （3）随着平板渗透到过渡区内的660公里不连续性或扁平化时，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的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛的影响来通过评估来支持的。

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