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

这个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理解俯冲带是如何对火山弧的位置负责的，以及这种深度和成分的条件是如何导致日本Hikurungi和阿拉斯加阿留申群岛等地区的地震的。该项目将建立一套3D模型和代码，这项工作将支持一名新研究人员和一名研究生。横波分裂测量结果表明，不同俯冲带间地幔楔的地震各向异性存在复杂的变化。上地幔的变形通过影响各向异性矿物的晶格优先取向（LPO）和弹性不同物质（如充液裂缝）的形状优先取向而引起地震各向异性。早期的三维俯冲模型研究表明，斜俯冲、三维板块几何形状和边缘曲率导致地幔楔流方向的复杂空间变化，可能产生复杂的横波分裂模式，并使分裂测量的解释变得困难。在这项研究中，研究人员和研究生将研究三维地幔楔流模式对LPO发育和地震各向异性的影响，特别是斜向俯冲的作用。他们将根据俯冲倾角、板块几何形状和边缘曲率计算地幔楔流场。利用计算得到的地幔流场计算LPO和横波分裂参数，将计算得到的分裂参数值与观测值进行比较，系统地量化这些因素对全球观测到的地幔楔各向异性结构的贡献。

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.