CSEDI Collaborative Research: 3D Temperature and Composition Structure of the Upper Mantle Using Seismological and Mineral Physics Constraints

CSEDI 合作研究：利用地震学和矿物物理约束的上地幔 3D 温度和成分结构

• 批准号: 0456112
• 负责人: Lars Stixrude
• 金额: $ 13.02万
• 依托单位: Regents of the University of Michigan - Ann Arbor
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-06-01 至 2007-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0456112&HistoricalAwards=false
• 关键词: CSEDI; Collaborative; Research; 3D; Temperature

This is a collaborative study between seismologists, mineral physicists and geodynamicists at UC Berkeley and at the Univ. of Michigan, the goal of which is to combine observational constraints and theoretical tools from their respectivefields and investigate large scale 3D variations in temperature and major element chemistry in the earth's upper mantle directly from the inversion of seismic waveforms. At the heart of this proposed study is the conjecture, supported by theoreticalconsiderations, that the one step inversion of seismic waveforms for physical parameters such as composition C and temperature T, should yield more stable results than the standard approach of first inverting for velocity and attenuation structure separately, and then interpreting the obtained maps in terms of physical parameters. The latter is currently inhibited by the poor resolution in 3D upper mantle attenuation, Q, due to contamination of amplitudes by largely unmodelled, butsignificant, effects of focusing and scattering. The coupled character of the equations in the one step approach, combined with the strong sensitivity of amplitudes to T (through anelastic terms) should offset the approximate character of the available mineral physics partial derivatives as well as the errors due to inadequate theoretical treatment of focusing.The investigators will: 1) invert a global collection of long period seismic waveforms for T and radial anisotropy, using recentexperimental contraints on dispersion and attenuation in the uppermost mantle; 2) starting from the model obtained in (1), they will test their ability to invert for lateral variations in composition (as expressed in terms of basalt depletion). Partial derivatives with respect to C and their uncertainties will be evaluated and provided by the mineral physicists in the team using a self-consistent formalism which incorporates results from experiments and first principles calculations. At this point, they will also incorporate geodynamical constraints to increase resolution of the compositional component of the inversion. An iterative procedure will be required at each step in the inversion process, because of the dependence of various partial derivatives on temperature, due to the presence of strong attenuation and phase changes, as well as the large uncertainties remaining in the estimation of these partial derivatives. The project includes funding for two students and a post doc, who will be trained using a cross-disciplinary approach.

这是加州大学伯克利分校和大学的地震学家，矿物物理学家和地球动力学家之间的一项合作研究。密歇根州的目的是将观察性约束和理论工具从各自场合结合在一起，并研究地球上层的大规模温度和主要元素化学的大规模3D变化，直接从地震波形的倒置中。 这项拟议的研究的核心是在理论上的支持下的猜想，即对物理参数（例如组成C和温度T）的地震波形的一步反转，应比第一次反转速度和衰减结构的标准方法更稳定，然后在物理参数中解释所获得的映射。目前，由于在3D上地幔衰减（Q）中的分辨率较差，由于振幅不大，但要点含量较大，但很明显地对聚焦和散射的影响抑制了Q。一步方法中方程的耦合特征，再加上振幅对t的强烈敏感性（通过词汇术语）应抵消可用的矿物质物理部分衍生物的近似特征关于最高地幔的分散和衰减； 2）从（1）中获得的模型开始，他们将测试其反转成分横向变化的能力（如玄武岩耗竭而表达）。 相对于C及其不确定性的部分导数将由团队中的矿物质学家使用自洽的形式主义进行评估和提供，该形式主义结合了实验和第一原则计算的结果。 在这一点上，他们还将结合地球动力学约束，以增加反转的组成部分的分辨率。 由于存在强大的衰减和相变，以及在这些部分衍生剂的估计中，由于存在各种部分导数对温度的依赖，因此在反转过程的每个步骤中都需要进行迭代程序。 该项目包括为两名学生和一名邮政文件提供资金，他们将通过跨学科方法对他们进行培训。