Mantle Dynamics of the Izu-Bonin Subduction System

本研究通过地震观测和数值模拟实验相结合，提供了伊豆-小笠原俯冲系统内地幔流动和动力学的新约束。 这项工作的结果提供了有关会聚边缘地幔过程的关键信息，包括地幔岩浆输送的方式以及构造板块和岩石圈下地幔之间应变分配的几何形状。1）伊豆-小笠原俯冲带上地幔各向异性的三维分布及其对应变分配和地幔流动的意义;（2）解释地震各向异性结果，特别是它们与地幔输运过程和构造板块与岩石圈下地幔耦合程度的关系。该项目的地震部分涉及一组独特的剪切相的剪切波分裂分析，包括局部S，sS-S差分分裂。 伊豆-小笠原地区特别适合拟议的地震研究，因为伊豆-小笠原地区发生的地震提供了一个极好的地震相数据集，对研究区域的大部分地区进行了采样。 伊豆-小笠原地震的宽频带波形的可用性已被许多高分辨率地震仪记录，并允许约束伊豆-小笠原系统的横向变化和各向异性的深度分布。该项目的数值模拟部分涉及计算一系列物理模型参数的地幔流三维模型。 为了确定地幔流动与地震各向异性观测的关系，正在使用流动模型来计算预测的各向异性，使用来自一系列变形研究的适当弹性参数值，并将建模结果与地震各向异性结果进行比较。

This study provides new constraints on mantle flow and dynamics within the Izu-Bonin subduction system through a combination of seismic observations and numerical modeling experiments. Results of this work are providing key information regarding mantle processes in convergent margins, including the means of mantle magma transport and the geometry of strain partitioning between tectonic plates and the sublithospheric mantle.In this coupled approach, the following issues are being addressed specifically: 1) the 3-D distribution of upper mantle anisotropy and its implications for strain partitioning and mantle flow in the Izu-Bonin subduction zone; and 2) the interpretation of seismic anisotropy results, particularly their relationship to both mantle transport processes and the degree of coupling between tectonic plates and sublithospheric mantle.The seismic component of the project involves shear wave splitting analysis for a unique set of shear phases, including local S, teleseismic SKS, and sS-S differential splitting. The Izu-Bonin region is particularly well-suited for the proposed seismic studies, as earthquakes generated in Izu-Bonin provide an excellent dataset of seismic phases that sample a broad portion of the study area. The availability of broadband waveforms of Izu-Bonin earthquakes have been recorded by many high-resolution seismographs and allows constraint of both lateral variations and the depth distribution of anisotropy for the Izu-Bonin system. The numerical modeling component of the project involves calculation of 3-D models of mantle flow for a range of physical model parameters. To determine the relationship of mantle flow to the seismic anisotropy observations, flow models are being used to calculate predicted anisotropy using appropriate elastic parameter values from a range of deformation studies, and comparing the modeling results with the seismic anisotropy results.