CSEDI: Collaborative Res: Toward Mapping 3D Variations in Temperature and Chemical Composition in the Upper Mantle through a Mineral Physics-Based Inversion of Seismic Waveforms

CSEDI：协作研究：通过基于矿物物理的地震波形反演绘制上地幔温度和化学成分的 3D 变化

• 批准号: 0112409
• 负责人: Barbara Romanowicz
• 金额: $ 10.5万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-08-15 至 2003-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0112409&HistoricalAwards=false
• 关键词: CSEDI; Collaborative; Res; Toward; Mapping

Romanowicz Karato This is a collaborative study between seismologists at UC Berkeley and mineral physicists at Yale University, to explore the feasibility of inverting seismic long period waveform data directly for 3D variations in effective temperature and major element chemistry in the upper mantle. Effective temperature will include the effects of temperature and water content, which cannot be easily separated from seismic data alone. Water content is likely to have large effects on rheology and therefore has significant influence on the dynamics of the Earth's mantle. They will use the mineral physics framework to delineate contributions from these various factors and provide estimates of relevant partial derivatives. Effects of major element chemistry can be distinguished from that of water, because water has a large influence on anelasticity whereas major element chemistry does not. On the other hand anelasticity is more strongly dependent on temperature than seismic velocity. At the heart of this study is the conjecture, supported by theoretical considerations, that the one step inversion of seismic waveforms for physical parameters such as composition C and (effective) temperature T*, should yield more stable results than the standard approach of first inverting for velocity and Q structure and then interpreting the obtained maps in terms of physical parameters. The latter is currently inhibited by the poor resolution in 3D upper mantle Q, due to contamination of amplitudes by largely unmodelled, but significant, effects of focusing and scattering. In the one step inversion the effects of C and T* are coupled in the inversion matrix elements, whereas in the standard approach, only the amplitudes depend on anelastic terms, while both phase and amplitudes depend on the elastic ones, leading to strong biases in the distribution of Q inferred. 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 and the errors due to inadequate theoretical treatment of focusing.

Romanowicz Karato这是加州大学伯克利分校的地​​震学家与耶鲁大学的矿物理学家之间的一项合作研究，以探索直接倒置地震长期波形数据的可行性，以实现有效的温度和高地幔中主要元素化学的3D变化。有效温度将包括温度和水含量的影响，这些效果不能仅仅与地震数据相分开。水含量可能对流变学有很大的影响，因此对地球地幔的动态产生了重大影响。他们将使用矿物物理框架从这些各种因素中描述贡献，并提供相关部分衍生物的估计。主要元素化学的影响与水的影响可以区分，因为水对弹性有很大影响，而主要元素化学却没有。另一方面，与地震速度相比，异弹性更大程度地取决于温度。这项研究的核心是由理论上考虑的猜想，即，与首先倒置速度和Q结构倒置的标准方法相比，对物理参数（例如组成C和（有效）温度T*）的地震波形的一步反转应产生更稳定的结果，然后在物理参数上解释所获得的映射。由于3D上地幔Q中的分辨率较差，后者由于振幅而受到振幅的污染，因此在很大程度上未建模但显着的焦点和散射作用。在一个步骤反转中，C和T*的效果在反转矩阵元件中耦合，而在标准方法中，只有振幅取决于无弹性术语，而相位和振幅都取决于弹性术语，从而导致弹性偏差，从而导致Q分布的质量强大。一步方法中方程的耦合特征，再加上振幅对t*的敏感性（通过无弹性术语），应抵消可用矿物物理学部分衍生物的近似特征，以及由于对聚焦的理论处理不足而引起的错误。