Seismological Constraints on Global Mantle Anisotropy

全球地幔各向异性的地震学约束

基本信息

  • 批准号:
    0838605
  • 负责人:
  • 金额:
    $ 26.07万
  • 依托单位:
  • 依托单位国家:
    美国
  • 项目类别:
    Continuing Grant
  • 财政年份:
    2009
  • 资助国家:
    美国
  • 起止时间:
    2009-02-01 至 2014-01-31
  • 项目状态:
    已结题

项目摘要

Technical Description: The goal of the proposed research is to determine the three-dimensional variations of azimuthal anisotropy in the upper 1000 km of the mantle, at the global scale. Seismic anisotropy, that is the dependence of seismic wave velocity on the direction of propagation or polarization, offers a more complete description of Earth's elastic structure than isotropic velocities alone, and may be a signal of mantle deformation. Therefore, it constitutes a unique way of understanding and constraining Earth?s interior. However, aside from the base of the mantle and the top of the upper mantle, little is known about mantle seismic anisotropy, mostly because of the reduced resolution of commonly used seismic data below ~250 km. The proposed work will take advantage of a new global surface wave dataset to model the three-dimensional changes in azimuthal anisotropy in the upper 1000 km of the mantle. These data are azimuthally anisotropic fundamental mode and overtone surface wave phase velocity maps for Love and Rayleigh waves, and because higher mode measurements are included these data have high sensitivity to the targeted deep structure. In order to constrain anisotropy, we will combine a traditional least-squares inverse technique with a model space search approach. This forward modeling method will enable us to determine the common properties of all the models that satisfy the data. It will therefore allow us to ascertain which model features are robust and which parameters trade-off with others, a key-element in making meaningful interpretation of the results.This project will enable us to determine the likelihood of presence of azimuthal anisotropy in the transition zone and the top of the lower mantle, how azimuthal anisotropy changes with depth, and how it differs beneath oceans and continents. To the extent we can relate seismic anisotropy to deformation, these results will be used to shed new light on (1) the geometry of mantle deformation, (2) whether and where sub-lithospheric deformation couples with plate motion, (3) the contribution to shear-wave splitting of present-day asthenospheric deformation versus fossil lithospheric deformation, and (4) the passive vs. active nature of mid-ocean ridges.Non-Technical Description: Our current knowledge of Earth?s deep mantle is poor, but essential to comprehend surface plate tectonics and how they relate to deformation at greater depths. The goal of this project is to improve our understanding of mantle deformation at large depths by mapping the three-dimensional directional dependence of seismic wave velocities, i.e. seismic anisotropy, down to depths of 1000 km. Seismic anisotropy is probably a signal of mantle deformation and therefore constitutes a unique tool to constraint its mineralogy, composition, and dynamics. Combined with mineral physics data and geodynamic modeling, it can help us understand the evolution of our planet.To reach our goal we will combine a new global seismic dataset with an innovative forward modeling method, which will help us explore many different types of models and select those that explain the data the best. With this computationally intensive approach we will be able to estimate model uncertainties, a key-element to make sensible interpretation of the results in terms of composition, mineralogy, and deformation. The models obtained will help constraining geodynamic models, and will guide mineral physics experiments trying to understand mantle deformation. Funding of this project will thus benefit a large part of the Earth science community. The results, methods and models will be shared with the broader audience and the seismological research community through scientific publications, conference presentations, and a website. In addition, the proposed research will provide support for a graduate student who will be trained and acquire knowledge in the fields of global seismic tomography, modeling techniques, and parallel computer programming.
技术描述:这项拟议研究的目标是在全球范围内确定地幔上部1000公里处方位各向异性的三维变化。地震各向异性,即地震波速度与传播方向或极化方向的关系,比各向同性速度更完整地描述了地球的弹性结构,并可能是地幔变形的信号。因此,它构成了一种独特的认识和制约地球的方式?S内心。然而,除了地幔底部和上地幔顶部之外,人们对地幔地震各向异性的了解很少,主要是因为常用的250公里以下的地震数据分辨率降低。这项拟议的工作将利用一个新的全球面波数据集来模拟地幔上部1000公里处方位各向异性的三维变化。这些数据是Love波和Rayleigh波的方位各向异性基模和泛音面波相速度图,由于包括了更高的模式测量,这些数据对目标深部结构具有很高的敏感性。为了抑制各向异性,我们将传统的最小二乘逆技术与模型空间搜索方法相结合。这种正向建模方法将使我们能够确定满足数据的所有模型的共同属性。因此,这将使我们能够确定哪些模型特征是稳健的,哪些参数与其他模型特征是权衡的,这是对结果进行有意义解释的关键因素。这个项目将使我们能够确定在过渡带和下地幔顶部存在方位各向异性的可能性,方位各向异性如何随深度变化,以及它在海洋和大陆之下的不同之处。在我们可以将地震各向异性与变形联系起来的范围内,这些结果将被用来阐明(1)地幔变形的几何学,(2)岩石圈以下变形是否与板块运动耦合以及在哪里耦合,(3)现代软流圈变形与化石岩石圈变形对剪切波分裂的贡献,以及(4)大洋中脊的被动与主动性质。非技术描述:我们目前对地球的了解?S深部地幔很差,但对于理解表层板块构造及其与更深层次变形的关系是必不可少的。该项目的目标是通过绘制深至1000公里的地震波速度的三维方向相关性,即地震各向异性,来提高我们对大深度地幔变形的理解。地震各向异性可能是地幔变形的信号,因此是制约其矿物学、成分和动力学的独特工具。结合矿物物理数据和地球动力学模型,它可以帮助我们了解地球的演化。为了实现我们的目标,我们将把一个新的全球地震数据集与创新的正演模拟方法结合起来,这将帮助我们探索许多不同类型的模型,并选择最能解释数据的模型。有了这种计算密集的方法,我们将能够估计模型的不确定性,这是从成分、矿物学和变形方面对结果进行合理解释的关键因素。所获得的模型将有助于约束地球动力学模型,并将指导试图了解地幔变形的矿物物理实验。因此,该项目的资金将使地球科学界的很大一部分人受益。结果、方法和模型将通过科学出版物、会议报告和网站与更广泛的受众和地震学研究社区共享。此外,拟议的研究将为一名研究生提供支助,该研究生将接受全球地震层析成像、建模技术和并行计算机编程领域的培训和获取知识。

项目成果

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Caroline Beghein其他文献

Evaluation of the InSightSeers and DART Boarders mission observer programmes
洞察者和 DART 登板者任务观察员方案的评估
  • DOI:
    10.1038/s41550-024-02434-1
  • 发表时间:
    2024-12-16
  • 期刊:
  • 影响因子:
    14.300
  • 作者:
    Benjamin Fernando;Claire Newman;Ingrid J. Daubar;Caroline Beghein;Nancy L. Chabot;Jessica C. E. Irving;Catherine L. Johnson;Mark P. Panning;Ana-Catalina Plesa;Andrew S. Rivkin;Sue Smrekar;W. Bruce Banerdt
  • 通讯作者:
    W. Bruce Banerdt

Caroline Beghein的其他文献

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{{ truncateString('Caroline Beghein', 18)}}的其他基金

Collaborative Research: Detecting Seismic Anisotropy in the Upper Mantle and Upper Mantle Transition Zone
合作研究:探测上地幔和上地幔过渡带的地震各向异性
  • 批准号:
    1446978
  • 财政年份:
    2015
  • 资助金额:
    $ 26.07万
  • 项目类别:
    Continuing Grant
Early Career: Acquisition of a Computer Cluster
早期职业生涯:购买计算机集群
  • 批准号:
    0949255
  • 财政年份:
    2010
  • 资助金额:
    $ 26.07万
  • 项目类别:
    Standard Grant

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