High-resolution seismic models of the upper mantle beneath the Indian Ocean

本研究探讨了构造板块的物理结构与下伏地幔的化学和部分熔融过程之间的关系，由此产生形成新板块的岩浆。过去的研究集中在快速扩张的太平洋，但在较慢的扩张速度和较低的岩浆供应形成的板块可能有不同的结构和不同类型的化学变化。对覆盖缓慢扩张的印度洋海盆的数据进行分析，将提供第一批地震和地球化学结果，其分辨率与太平洋的分辨率相似。比较将区分板块老化的全球特征和反映特定盆地岩浆发展的区域特征，将建立印度洋下上地幔地震速度、衰减和径向各向异性的区域模型。将确定平均年龄相关的地震结构和偏离平均值。将只使用位于印度洋内或印度洋边缘的地震和地震台站，以避免穿过大陆上地幔的路径很长。对于弹性和滞弹性地震模型，将测量和联合反演基模和高模表面波的频率相关相位和振幅。这种方法利用振幅对短波长结构的敏感性，以允许以自洽的方式估计衰减和剪切速度。将通过解释地震模型以及现有的矿物物理学、大洋中脊玄武岩成分和测深数据来估计地幔温度、部分熔融物含量和上地幔成分。这项研究将是博士论文的基础，本科生也将参与研究的各个方面。

This study addresses the relationship between the physical structure of tectonic plates and the chemistry and partial melting processes of the underlying mantle, from which magma that forms new plates is generated. Past studies have focused on the fast-spreading Pacific but plates formed at slower spreading rate and lower magma supply may have different structure and different types of chemical variability. Analysis of data covering the slow-spreading Indian Ocean basin will provide the first seismic and geochemical results at a resolution similar to that available for the Pacific. Comparison will distinguish characteristics that are global features of plate aging versus regional features reflecting a particular basin's magmatic development.Regional models of upper mantle seismic velocity, attenuation, and radial anisotropy beneath the Indian Ocean will be developed. Both the average age-dependent seismic structure and deviations from the average will be determined. Only earthquakes and seismic stations located within or on the margins of the Indian Ocean will be used, to avoid paths with significant length through continental upper mantle. Frequency-dependent phase and amplitude of fundamental-mode and higher-mode surface waves will be measured and jointly inverted for elastic and anelastic seismic models. This approach takes advantage of the amplitude sensitivity to short wavelength structure to allow estimation of attenuation and shear velocity in a self-consistent manner. Mantle temperature, partial-melt content, and composition of the upper mantle will be estimated by interpreting the seismic models together with existing mineral physics, mid-ocean-ridge basalt composition, and bathymetry data. The research will be the basis of a PhD thesis and undergraduates will also be involved in aspects of the research.