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和耶鲁大学的矿物物理学家之间的合作研究，旨在探索直接反演地震长周期波形数据的可行性，以获得上地幔有效温度和主要元素化学的三维变化。有效温度将包括温度和含水量的影响，这不能简单地从地震数据中分离出来。水含量可能对流变学有很大的影响，因此对地幔的动力学有重要的影响。他们将使用矿物物理学框架来描述这些不同因素的贡献，并提供有关偏导数的估计数。主元素化学的影响可以与水的影响区分开来，因为水对滞弹性有很大的影响，而主元素化学则没有。另一方面，滞弹性对温度的依赖性比地震速度更强。在这项研究的核心是推测，支持理论上的考虑，一步反演地震波形的物理参数，如组成C和（有效）温度T*，应产生更稳定的结果比标准的方法，首先反演速度和Q结构，然后解释所获得的地图的物理参数。后者目前被抑制在3D上地幔Q的分辨率差，由于污染的振幅在很大程度上未建模，但显着的，聚焦和散射的影响。在一步反演中，C和T* 的影响在反演矩阵元素中耦合，而在标准方法中，只有振幅取决于滞弹性项，而相位和振幅都取决于弹性项，从而导致推断的Q分布的强烈偏差。一步法中方程的耦合特性，结合振幅对T* 的强敏感性（通过滞弹性项），应抵消可用矿物物理偏导数的近似特性和由于聚焦的理论处理不足而引起的误差。