CSEDI Collaborative Proposal: a multi-disciplinary investigation of slab deformation and resulting seismic anisotropy from the transition zone to the base of the mantle

CSEDI 合作提案：对板片变形和由此产生的从地幔底部过渡带的地震各向异性进行多学科研究

• 批准号: 2054926
• 负责人: Mingming Li
• 金额: $ 27.84万
• 依托单位: Arizona State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-01 至 2024-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2054926&HistoricalAwards=false
• 关键词: CSEDI; Collaborative; Proposal; multi; disciplinary

Over geological time scales, rocks in Earth’s deep interior flow like fluids. The deformation and advection of rocks within the Earth are concrete expressions of mantle thermal convection. Mantle convection drives plate tectonics near Earth’s surface and controls the long-term evolution of the planet. For this project, a team of scientists from different research fields - including seismology, mineral physics, and geodynamics - collaborate to better understand the nature of mantle convection. When earthquakes happen, the energy propagates through Earth’s interior in the form of seismic waves. The speed of seismic waves traveling through rocks in one direction is often different from that in another direction. This phenomenon is called seismic anisotropy. Seismic anisotropy of rocks is controlled by their mineral structure and the nature of the surrounding mantle flows. Here, the researchers use super-computers to simulate mantle flow fields. They perform mineral physics experiments to study the deformation mechanisms of mantle minerals. They analyze seismic waves to understand mantle seismic anisotropy. The predicted mantle flow fields are combined with new understanding of mineral deformation to predict seismic anisotropy, which is then compared with observations. The aim is to provide new insight into the structure and dynamics of Earth’s deep interior. This project fosters inter-disciplinary collaboration and provides support to 3 graduate students, 1 postdoctoral associate and 1 early-career scientist. Teaching materials will be produced, which will be used in undergraduate and graduate classes and in educational outreach to the public through outreach events and via the internet. Analytical and modeling software will become available to general users.Over the past few decades, seismic anisotropy has been observed mainly in Earth’s uppermost and lowermost mantle. Yet, accumulating evidence suggests the presence of significant seismic anisotropy in the transition zone and the uppermost lower mantle. The nature of uppermost mantle seismic anisotropy is relatively well established, and some consensus exists to first order on the large-scale distribution of anisotropy in D". There is, however, little consensus on the character and strength of seismic anisotropy in the mantle transition zone and the uppermost lower mantle. It remains unclear at these depths how seismic anisotropy is related to mantle flow and the deformation mechanisms of mantle minerals. Interpreting seismic observations in the context of mantle dynamics requires input from mineral physicists and geodynamicists; they can relate the seismic velocities and anisotropy to temperature, composition, and deformation of the corresponding materials. Here an interdisciplinary team of seismologists, geodynamicists, and mineral physicists aim to further advance the understanding of the seismic and viscosity structures, and the nature of mantle flow in two regions: 1) the D" layer, in continuation of their previous works; (2) the extended transition zone located at depths ranging from ~400 to 1000 km within the Earth.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.

在地质时间尺度上，地球内部深处的岩石像流体一样流动，地球内部岩石的变形和平流是地幔热对流驱动地球表面附近板块构造并控制地球长期演化的具体表现。在这个项目中，来自不同研究领域（包括地震学、矿物物理学和地球动力学领域）的科学家团队合作，以更好地了解地震发生时地幔对流的本质。地震波以地震波的形式在地球内部传播。地震波在一个方向上传播的速度通常与在另一个方向上传播的速度不同，这种现象称为岩石的地震各向异性。在这里，研究人员使用超级计算机模拟地幔流场，以研究地幔矿物的变形机制。了解地幔地震各向异性。将预测的地幔流场与对矿物变形的新认识相结合，以预测地震各向异性，然后与观测结果进行比较，该项目旨在为地球深层的结构和动力学提供新的见解。跨学科合作，并将为 3 名研究生、1 名博士后助理和 1 名早期职业科学家提供支持，这些材料将用于本科生和研究生课程以及通过外展向公众进行教育推广。分析和建模软件将可供普通用户使用。在过去的几十年中，主要在地球的最上层和最下层地幔中观察到了地震各向异性，然而，越来越多的证据表明在转变过程中存在显着的地震各向异性。上地幔地震各向异性的性质已经相对明确，并且对于各向异性的大尺度分布存在一些共识。 D"。然而，对于地幔过渡带和下地幔最上部的地震各向异性的特征和强度还没有达成共识。在这些深度，地震各向异性与地幔流和地幔矿物变形机制的关系仍不清楚。在地幔动力学背景下解释地震观测需要矿物物理学家和地球动力学家的输入；他们可以将地震速度和各向异性与温度、成分、由地震学家、地球动力学家和矿物物理学家组成的跨学科团队旨在进一步推进对两个区域的地震和粘性结构以及地幔流性质的理解：1）D”层，位于延续他们之前的工作；(2) 位于地球深度约 400 至 1000 公里的扩展过渡区。该奖项反映了 NSF 的法定使命，并被认为是值得的。通过使用基金会的智力优势和更广泛的影响审查标准进行评估来提供支持。

项目成果

The influence of uncertain mantle density and viscosity structures on the calculations of deep mantle flow and lateral motion of plumes

不确定的地幔密度和粘性结构对深部地幔流和地幔柱横向运动计算的影响

• DOI: 10.1093/gji/ggad040
• 发表时间: 2023-01
• 期刊: Geophysical Journal International
• 影响因子: 2.8
• 作者: Li; Mingming
• 通讯作者: Mingming