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

贝斯·格兰德研究人员提议一名矿物物理学家(伊利诺伊大学厄巴纳-香槟分校的J·巴斯)和一名地震学家(德克萨斯大学奥斯汀分校的S·格兰德)合作，旨在阐明地球300-1000公里深处过渡带的地震结构和矿物学。地震结构将在几个地区确定，具有前所未有的分辨率，跨越过渡带不连续的速度跳跃和跳跃之间的地震速度梯度。有关矿物体系的现有矿物弹性数据和相关系将被用来计算各相的组成和比例，以及作为一系列块体成分范围内深度的函数的候选地幔组合的性质。将对β相和铝钙钛矿的高温高压弹性进行两个关键实验，以填补弹性数据库中最紧迫的空白。一种新的波形反演码将被用来确定矿物学模型在某些强加的约束下直接与地震数据的可接受的拟合度。例如，在橄榄石成分百分比和不连续面大小固定的情况下，他们可以搜索满足地震约束的允许的梯度模型。还将尝试其他初始条件。通过这种方式，研究人员建议以比以前更正式的定量方式来定义过渡带的结构和矿物学模型的范围，这些模型与地震数据相一致。这项研究将涉及UIUC的一名学生从事该项目的矿物物理方面的工作，以及UTA的一名从事地震学方面的学生。

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.