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合作研究。密歇根州的研究人员，其目标是结合各自领域的观测限制和理论工具，直接通过地震波形的反演来研究地球上地幔温度和主要元素化学的大规模 3D 变化。 这项研究的核心是由理论考虑支持的猜想，即成分 C 和温度 T 等物理参数的地震波形的一步反演应该比速度和衰减的第一次反演的标准方法产生更稳定的结果分别结构，然后根据物理参数解释获得的图。后者目前受到 3D 上地幔衰减 Q 分辨率较差的抑制，这是由于很大程度上未建模但显着的聚焦和散射效应对振幅的污染。一步法中方程的耦合特性，加上振幅对 T（通过滞弹性项）的强烈敏感性，应抵消可用矿物物理偏导数的近似特性以及由于聚焦理论处理不充分而产生的误差研究人员将：1）利用最近对最上地幔色散和衰减的实验限制，反演 T 和径向各向异性的长周期地震波形的全球集合； 2）从（1）中获得的模型开始，他们将测试其反演成分横向变化（以玄武岩损耗表示）的能力。 关于 C 的偏导数及其不确定性将由团队中的矿物物理学家使用自洽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理计算的结果。 此时，他们还将纳入地球动力学约束，以提高反演成分成分的分辨率。 由于各种偏导数对温度的依赖性、强衰减和相位变化的存在以及这些偏导数的估计中仍然存在很大的不确定性，反演过程中的每一步都需要迭代过程。 该项目包括资助两名学生和一名博士后，他们将接受跨学科方法的培训。