Compressional Wave Velocities of Pollycrystalline Mantle Materials at High Pressures Using Brillouin Spectroscopy

我们对地球内部的了解大多是基于地震学观测的推断。地震学对地幔的各向同性弹性特性提出了直接的限制。将实验室数据与地球地震模型进行比较，使人们对地幔的组成产生了许多猜想。通常，矿物的实验室数据仅限于体积模量和密度，而剪切模量的测量仍然非常稀少，特别是在高压下。PI将使用布里渊散射和金刚石砧细胞测量几种多晶硅酸盐的纵波速度。根据这些数据和材料的体积模量和密度的知识，可以用基本热力学计算出高压下的剪切模量。这些数据将使我们能够利用目前未被充分利用的地震信息，并有望对地幔的组成进行更严格的限制。

Most of what we know about the Earth's interior is based on inferences from seismological observations. Seismology places direct constraints on the isotropic elastic properties of the Earth's mantle. The comparison of laboratory data with seismic models of the Earth has led to much conjecture about the composition of the mantle. Typically, the laboratory data on minerals is constrained to the bulk modulus and the density, while measurements of the shear modulus remain very sparse, particularly at high pressures. The PI will measure the compressional wave velocities of several silicates in polycrystalline form, using Brillouin scattering and the diamond anvil cell. From this data and a knowledge of the bulk modulus and density of the material the shear moduli at high pressures can be calculated using elementary thermodynamics. These data will allow us to take advantage of the seismological information that is currently under-utilized, and hopefully will place tighter constraints on the composition of the Earth's mantle.