CSEDI Collaborative Res.: Composition and Seismic Structure of the Mantle Transition Zone

研究人员提出了一个矿物物理学家（J Bass，伊利诺伊大学厄巴纳-香槟分校）和地震学家（S. Grand，德克萨斯大学奥斯汀分校）的合作项目，旨在从300-1000公里的深度阐明地球过渡带的地震结构和矿物学。通过对跨过渡带不连续面的速度跳变和跳变之间的地震速度梯度的空前分辨率，将确定几个地区的地震构造。现有的矿物弹性数据和相关矿物系统的相关系将用于计算各个相的组成和比例，以及候选地幔组合的性质作为一系列大块组成的深度函数。为了填补弹性数据库中最紧迫的空白，我们将进行β相和铝钙钛矿高温高压弹性的两个关键实验。一种新的波形反演代码将用于确定矿物学模型在一定限制条件下直接与地震数据的可接受拟合。例如，在确定了橄榄石成分的百分比和不连续面大小后，他们可以搜索满足地震约束的允许梯度模型。其他初始条件也将被尝试。通过这种方式，研究人员建议以比以前更正式的定量方式定义过渡带的结构和与地震资料相适应的矿物学模型范围。这项研究将涉及一名学生在UIUC从事该项目的矿物物理方面的工作，一名学生在UTA从事地震学方面的工作。

Bass Grand The investigators propose a collaborative effort between a mineral physicist (J Bass, University of Illinois Urbana-Champaign) and a seismologist (S. Grand, University of Texas, Austin) aimed at elucidating the seismic structure and mineralogy of the Earth's transition zone, from 300-1000 km in depth. The seismic structure will be determined in several regions with unprecedented resolution of the velocity jumps across transition zone discontinuities and the seismic velocity gradients between the jumps. The available mineral elasticity data and phase relations for relevant mineral systems will be used to calculate the compositions and proportions of individual phases, and the properties of candidate mantle assemblages as a function of depth for a range of bulk compositions. Two key experiments on the high temperature and pressure elasticity of beta phase and aluminous perovskite will be done to fill in the most pressing gaps in the elasticity data base. A new waveform inversion code will be used to determine acceptable fits of mineralogic models directly to the seismic data within certain imposed constraints. For example, with the percent olivine component and size of discontinuities fixed, they can search for allowable models of gradients that satisfy seismic constraints. Other initial conditions will be tried as well. In this way the investigators propose to define both the structure of the transition zone and the range of mineralogical models which are compatible with the seismic data in a more formal quantitative way than has been done before. This research will involve one student working on mineral physics aspects of the project at UIUC, and a student working on the seismological aspects at UTA.