Collaborative Research: CSEDI: Integrating Seismic Anisotropy, Mantle Flow, and Rock Deformation in Subduction Zone Settings

俯冲带是一个构造板块俯冲到另一个板块之下的地方。它们是板块构造的重要组成部分，也是最危险的地震和火山的背景。俯冲板块上下的地幔流动是由俯冲板块的运动驱动的。研究俯冲带地幔流动的主要工具是测量地震波速的方向相关性。波速的变化--称为地震各向异性--源于地幔流动引起的矿物排列。然而，这项技术需要将地震观测与地幔流动背景下变形岩石中矿物颗粒排列的数据联系起来。在这里，该团队将最先进的岩石变形实验与地幔流动模型和地幔岩石中的地震各向异性模型相结合。他们产生的合成地震波与阿拉斯加、卡斯卡迪亚和南美的观测结果进行了比较。总体目标是提高对俯冲带中地幔流动的理解，并更好地约束板块构造。该项目为在丰富的跨学科环境中接受培训的研究生和本科生提供支持。它还促进了对K-12学生和教师的接触。项目成果将与社区分享，特别是通过关于这一主题的多学科会议。项目活动提供了俯冲带中地幔流动、橄榄石结构发育和地震各向异性观测的整体视图。该项目围绕三项任务进行组织。首先，研究人员使用圣路易斯华盛顿大学的大体积扭转(LVT)设备进行了一组新的高压和高温橄榄石变形实验。目的是确定菌株如何产生并随后改变晶体择优取向(CPO)。他们使用这些结果来产生一套经过实验验证的参数，用于D-Rex纹理建模程序，该程序模拟橄榄石CPO的形成和演化。其次，更新的D-Rex模型被合并到新的俯冲带3D模型中；这些模型使用了非线性流变学和一套关于俯冲带中水分布的替代假设。第三，该团队利用数值模拟俯冲带的结果，利用全波场模拟技术，模拟地幔楔形和次板块地幔中的横波分裂。通过这些步骤，研究人员定义了现有和新数据支持的对俯冲带附近地幔流动的潜在解释的集合。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Subduction zones are locations where one tectonic plate dives underneath another. They are an essential component of plate tectonics and the setting of the most hazardous earthquakes and volcanoes. Mantle flow above and below the subducting plate is driven by the motion of the subducting slab. The primary tool for investigating mantle flow at subduction zones is measuring the directional dependence of seismic wave speeds. Variations in wave speeds - called seismic anisotropy - arise from the alignment of minerals caused by mantle flow. However, this technique requires linking seismic observations to data on the alignment of mineral grains in deformed rocks, in the context of mantle flow. Here, the team combines state-of-the art rock-deformation experiments with models of mantle flow and models of seismic anisotropy in mantle rocks. They generate synthetic seismic waves that are compared with observations in Alaska, Cascadia, and South America. The overarching goal is to improve the understanding of mantle flow in subduction zones and better constrain plate tectonics. The project provides support for graduate and undergraduate students trained in a rich interdisciplinary environment. It also fosters outreach to K-12 students and teachers. The project outcomes will be shared with the community, notably through a multi-disciplinary conference on this topic. The project activities yield a holistic view of mantle flow, olivine texture development, and seismic anisotropy observations in subduction zones. The project is organized around three tasks. First, the researchers conduct a new set of high pressure and temperature olivine deformation experiments using the Large Volume Torsion (LVT) apparatus at Washington University in St. Louis. The aim is to determine how strain produces and subsequently modifies crystallographic preferred orientation (CPO). They use these results to produce a suite of experimentally validated parameters for use in the D-Rex texture modeling program, which simulates the formation and evolution of olivine CPO. Second, the updated D-Rex model is incorporated into new 3D models of subduction zones; these models use a nonlinear rheology and a set of alternative assumptions on the distribution of water in subduction zones. Third, the team uses the results of the numerically modeled subduction zones to simulate shear wave splitting in the mantle wedge and sub-slab mantle, using full-wavefield simulation techniques. Through these steps, the researchers define an ensemble of potential interpretations of mantle flow near subduction zones that are supported by existing and new data.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.