Two-stage Deformation of Olivine: Effects of Deformation History on Seismic Anisotropy

板块构造的特征是覆盖地球表面的刚性移动地貌或板块。 这些板块的运动从根本上改变了地球的地貌。此外，板块运动是地震、海啸和许多其他自然灾害的主要原因。 这种板块运动的驱动力是地幔的缓慢对流。地球物理学的一个基本问题是了解地幔对流的流动模式，以及它们如何与移动的板块相互作用。 为了推断这些流动模式，我们使用地震学的工具来探测地球内部由岩石变形产生的结构。 拟议研究的目的是调查我们如何从地震数据中推断流动模式的细节。 密集的地震台网和高分辨率的地震各向异性测量为深入了解地幔变形，特别是在板块边界附近的地幔变形提供了新的机会。 然而，要解释地震各向异性的流动模式的地震各向异性和变形运动学之间的关系，必须了解。 大部分地震各向异性是由橄榄石的晶格择优取向（LPO）产生的，它是响应于渐进变形而形成和演化的。 演化的模式和速率取决于变形的物理化学条件及其对微物理变形和恢复的影响。 在这些项目中，我们正在研究几个因素，包括（1）温度，（2）粒度和（3）预先存在的LPO对织构发展的作用。 我们的主要重点将放在矿物橄榄石，它产生了大部分的地震各向异性在上地幔。 我们将进行实验，以了解不同的实验室条件下的微观结构演变的敏感性，并促进外推到地球。 在这些实验中收集的数据将为解释地震各向异性提供新的背景，特别是在复杂的运动学环境中。

Plate tectonics is characterized by rigid, moving landforms, or plates, which cover Earth's surface. The motion of these plates fundamentally alters the landscape of the planet. Moreover, plate motions are primarily responsible for earthquakes, tsunamis, and many other natural hazards. The driving force for this plate motion is the slow convection of Earth's mantle. A fundamental problem in geophysics is understanding the flow patterns of mantle convection, and how they interact with moving plates. To infer these flow patterns, we use the tools of seismology to detect structures in Earth's interior that are produced by the deformation of rocks. The objective of the proposed research is to investigate details of how we infer flow patterns from seismological data. Dense seismic networks and high resolution measurements of seismic anisotropy provide new opportunities for insight into mantle deformation, particularly in the vicinity of plate boundaries. However, to interpret seismic anisotropy in terms of flow patterns the relationship between seismic anisotropy and deformation kinematics must be understood. Most seismic anisotropy is generated by the lattice-preferred orientation (LPO) of olivine, which forms and evolves in response to progressive deformation. The pattern and rate of evolution depends on the physiochemical conditions of deformation, and its effects on microphysical deformation and recovery. In these projects, we are investigating several factors, including the role of (1) temperature, (2) grain-size, and (3) pre-existing LPO, on texture development. Our primary focus will be on the mineral olivine, which produces most of the seismic anisotropy in the upper mantle. We will conduct experiments to understand the sensitivity of microstructural evolution to different laboratory conditions and to facilitate extrapolation to Earth. Data collected in these experiments will provide a new context for the interpretation of seismic anisotropy, especially in complex kinematic settings.