3-D Mantle wedge flow pattern and seismic anisotropy: Effects of oblique subduction

3-D 地幔楔流模式和地震各向异性：倾斜俯冲的影响

• 批准号: 1620604
• 负责人: Ikuko Wada
• 金额: $ 13.37万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1620604&HistoricalAwards=false
• 关键词: Mantle; wedge; flow; pattern; seismic

This project looks to improve our understanding of the inner workings of subduction zones. The particular focus of this work on modeling the interface of two colliding plates, the mantle wedge, can help us to better understand how subduction zones are responsible for the location of volcanic arcs and how the conditions at that depth and composition can lead to earthquakes in areas like Hikurungi, Japan and the Aleutians, Alaska. The project will build a suite of 3D models and codes that The work will support a new researcher and a graduate student.Shear waves splitting measurements indicate complex variations in the seismic anisotropy of the mantle wedge among different subduction zones. Deformation in the upper mantle causes seismic anisotropy through its effect on the lattice-preferred orientation (LPO) of anisotropic minerals and shape-preferred orientation of elastically distinct material, such as fluid-filled cracks. Earlier 3-D subduction modeling studies indicate that oblique subduction, 3-D slab geometry, and margin curvature cause complex spatial variations in mantle wedge flow directions, likely generating complex shear wave splitting patterns and making the interpretation of splittingmeasurements difficult. In this study the researcher and graduate student will investigate the effect of 3-D mantle wedge flow patterns on the development of LPO and seismic anisotropy, focusing particularly on the role of oblique subduction. They will calculate mantle wedge flow fields for a range of subduction obliquity, slab geometry, and margin curvature. Using the calculated mantle flow field to compute LPO and shear wave splitting parameters the work will compare the calculated splitting parameter values with observation to systematically quantify the contributions of these factors to the observed anisotropic structures of mantle wedges globally.

该项目旨在提高我们对俯冲带内部运作的理解。这项工作的重点是模拟两个碰撞板块的界面，地幔楔，可以帮助我们更好地了解俯冲带如何对火山弧的位置负责，以及该深度和成分的条件如何导致日本Hikurungi和阿拉斯加阿留申群岛等地区的地震。 该项目将建立一套3D模型和代码，这项工作将支持一个新的研究人员和一个研究生。剪切波分裂测量表明，在不同的俯冲带之间的地幔楔的地震各向异性的复杂变化。上地幔的变形通过影响各向异性矿物的晶格优选取向（LPO）和弹性不同材料（如充满流体的裂缝）的形状优选取向而引起地震各向异性。早期的3-D俯冲模拟研究表明，斜俯冲，3-D板的几何形状，和边缘曲率造成复杂的空间变化地幔楔流方向，可能会产生复杂的剪切波分裂模式，使splittingmeasurements的解释困难。在这项研究中，研究人员和研究生将调查的3-D地幔楔流模式的发展LPO和地震各向异性的影响，特别是侧重于斜俯冲的作用。他们将计算一系列俯冲带、板块几何形状和边缘曲率的地幔楔流场。使用计算的地幔流场计算LPO和剪切波分裂参数的工作将比较计算的分裂参数值与观测，系统地量化这些因素的贡献，所观察到的地幔楔的各向异性结构的全球。