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

绘制由海洋岩石圈下降引起的地幔流图对认识俯冲过程具有重要意义。根据室内实验、地幔流动计算机模拟和横波分裂测量，提出了俯冲诱发地幔流动的两种基本类型。然而，到目前为止，这些流动模式在实际俯冲环境中不同深度的行为仍然难以捉摸。在这个项目中，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动环流模式：中美洲、加勒比、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热化学演化的认识。此外，中美洲、卡斯卡迪亚和地中海是世界上地震活动最活跃的地区之一。利用新的三维层析模型，研究小组将数值模拟地球对这些地区过去和未来发生的一些大地震的反应，这可能为人口稠密地区的地震危险提供有价值的信息。该项目将通过支持一名早期职业PI和一名博士研究生来推进德克萨斯大学达拉斯地震成像实验室的发展。该项目的成果将通过同行评议的出版物和在国家/国际会议上的发言加以传播。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三维方位各向异性结构。这种反演策略提供了一个统一的框架，可以同时约束多个地震参数，并使团队能够通过将记录波形与全波场建模结果拟合，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面波结合起来，同时约束从地壳到过渡带的波速和方位各向异性。通过研究波速异常与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)在弧后、弧前和亚板块区域的不同深度，极向和环向模式的地幔流是如何相互竞争和干扰的？(2)板块分离和撕裂对地幔流动循环的影响是什么？(3)当板块穿过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。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.