Integrating the LPO Constraint into 3D Subduction Dynamics Simulations

俯冲是指一个构造板块下沉到另一个构造板块之下，进入地幔的过程。俯冲带是地球上构造和地震最活跃的地区之一。它们有大的破坏性地震和丰富的火山活动。这种地质活动是由下沉的构造板块驱动的，这导致了周围地幔的变形（应力的积累）和融化。这些地下过程是用地球物理和地球化学方法间接观测到的。在这些观测中，只有地震各向异性可以直接与俯冲板块下沉引起的变形的空间格局联系起来。为了将地震各向异性的观测结果与地幔的变形联系起来，科学家们需要计算出变形岩石中形成的一种结构，这种结构被称为晶格优先取向（LPO）。拟进行的研究将模拟俯冲作用来预测LPO构造。这是LPO计算第一次被完全整合到大规模三维模拟中。通过对这些结果的分析，研究人员将根据浅层地幔的三维变形提供更好的地震各向异性观测解释。更好地了解地幔变形（应力）对于解决俯冲带地震和火山活动引起的自然灾害具有重要意义。为该项目开发的所有计算模块都将公开，以推进该项目以外的类似研究。该项目将培养一名博士生，学习计算建模、复杂系统分析以及如何将科学成果传达给广泛的受众。该项目还将为本科生提供研究机会，培养他们在批判性思维、项目开发、领导能力和科学方法方面的技能。拟议的研究将使用地幔模拟代码ASPECT创建、运行和分析大约16,3 -d的时间相关俯冲模拟，并使用示踪粒子和运动学（D-Rex） LPO计算对整个模型域的LPO结构演化进行全面集成计算。将对这些模型进行分析，以确定与确定俯冲系统的不同参数（物理性质、几何形状）相关的LPO结构特征。它们还将被分析，以确定与俯冲阶段和板块变形状态有关的LPO构造模式。对地表观测到的地震各向异性的预测将用于设计与卡斯卡迪亚、南美和中美洲俯冲带的一般特征相匹配的模型子集。然后，研究人员将比较预测和观测到的地震各向异性，以确定观测结果与地幔流动和板块变形之间的关系。研究生研究员将主要负责创建、运行和处理模拟，以及根据俯冲系统参数和俯冲阶段/状态分析结果。PI将主要负责编写后处理代码，从ASPECT获取LPO结构，计算弹性张量和由此产生的地震各向异性，并将这些预测与三个位置的观测结果进行比较。他们预计将发表至少六份包含该项目的主要发现的手稿。

Subduction is the process by which one tectonic plate sinks beneath another tectonic plate into the Earth's mantle. Subduction zones are some of the most tectonically and seismically active areas on the planet. They have large destructive earthquakes and abundant volcanic activity. This geologic activity is driven by the sinking tectonic plate, which causes deformation (build up of stresses) and melting in the surrounding mantle. These subsurface processes are observed indirectly using geophysical and geochemical methods. Of these observations, only seismic anisotropy can be directly linked to the spatial pattern of deformation caused by sinking of the subducted plate. To make the link from observations of seismic anisotropy to deformation in the mantle scientists need to calculate a fabric that develops in the deformed rocks called lattice-preferred orientation (LPO). The proposed research will simulate subduction to predict the LPO structure. This is the first time LPO calculations will be fully incorporated into large-scale 3-D simulations. By analyzing these results the investigators will provide better interpretations of seismic anisotropy observation in terms of the 3-D deformation in the shallow mantle. A better understanding of the mantle deformation (stresses) is important for addressing natural hazards due to earthquakes and volcanic activity in subduction zones. All of the computational modules developed for the project will be made publicly available to advance similar studies beyond this project. The project will train a PhD student in computational modeling, analysis of complex systems and how to communicate scientific results to a broad audience. The project will also provide research opportunities for undergraduates to develop their skills in critical-thinking, project development, leadership, and the scientific method.The proposed research will create, run and analyze approximately 16, 3-D, time-dependent simulations of subduction using the mantle simulation code ASPECT, with fully-integrated calculations of the evolution of LPO structure throughout the model domain using tracer particles and a kinematic (D-Rex) LPO calculation. The models will be analyzed to identify features in the LPO structure that are related to different parameters (physical properties, geometry) defining the subduction system. They will also be analyzed to identify patterns in the LPO structure related to the phase of subduction and state of deformation in the slab. Predictions of seismic anisotropy observed at the surface will be made for a subset of models designed to match the general characteristics of the Cascadia, S. America and Middle America subduction zones. The investigators will then compare the predicted and observed seismic anisotropy to determine how the observations are related to flow in the mantle and deformation of the slab. The graduate student researcher, will be primarily responsible for creating, running, and processing simulations, as well as the analysis of the results in terms of subduction system parameters and phase/state of subduction. The PI will be primarily responsible for writing the post-processing codes that takes the LPO structure from ASPECT, calculates the elastic tensor and resulting seismic anisotropy, and for the comparison of these predictions to observations from three locations. They anticipate publication of at least six manuscripts with the major findings of the project.