Dynamic Linkages between the Transition Zone & Surface Plate Motions in 3D Models of Subduction

过渡区之间的动态联系

• 批准号: 1246864
• 负责人: Magali Billen
• 金额: $ 26.71万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-01-01 至 2016-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1246864&HistoricalAwards=false
• 关键词: Dynamic; Linkages; between; Transition; Zone

The motion of tectonic plates at the surface of the earth is caused by forces within the earth's mantle: the push of positive buoyancy at spreading ridges and the pull of sinking plates (slabs) at subduction zones. At the earth's surface these forces result in earthquakes where the two plates slide past one another (plate boundaries). The ability of the force from sinking slabs to effectively pull tectonic plates behind them depends on how the slab deforms within the earth's mantle, which in turn depends on how its material properties change as it deforms. In addition, the total force associated with the sinking slab depends on changes in the crystal structure of the minerals (phase changes), which lead to changes in density within the slab. Most of these phase changes occur between 410 and 660 km beneath the earth's surface, a region known as the transition zone. Ultimately, the deformation of the sinking slab inside the mantle is manifest in seismicity occurring within the slab to depths of 660 km beneath the earth's surface, and observables changes in plate motions at the earth's surface. The purpose of this study is determine, 1) how surface plate motions and the state of stress within surface plates react to, and provide feedbacks for, slab dynamics in the transition, 2) what is the origin of deep slab seismicity, and 3) if the observed shape of slabs is related to intrinsic properties of the subducting plate and plate boundary, or is instead a reflection of the time-dependent evolution of the slab. While the focus of this study is on deformation within the earth?s mantle, this deformation couples to the motions of plates at the earth's surface, which can cause destructive earthquakes and tsunamis.To address these questions with will develop three-dimensional numerical models (simulations) of subduction dynamics. More specifically we will use the best laboratory and observational constraints on the mineral composition of the plate (the crust, the residual harzburgite and the mantle layers), phase transitions (including all major mineral components) and rheology of the plate and mantle. We will enable dynamically mobile plates and plate boundaries, which are essential for understanding the physical connection between slab deformation and surface plate motions. These models eliminate several simplifying assumptions used in previous studies allowing us to make connections between slab deformation and surface plate motions and slab seismicity. Model results will be compared to global data sets on slab shape, plate characteristics and kinematics, as well as regional seismic observations on the state of stress within slabs and seismic discontinuities (which occur at phase transitions) across subducting lithosphere. The results of this project will provide a much more complete and realistic understanding of the physical processes that control the deformation of slabs and their ability to pull tectonic plates, and insight into how slab seismicity is related to the larger scale deformation slabs. In addition, the research will support the training of a PhD student, contribute software to the modeling community, introduce undergraduate students to scientific research, and contribute to the material used in undergraduate instruction.

地球表面构造板块的运动是由地幔内部的力引起的：扩张脊处正浮力的推动和俯冲带处下沉板块（板片）的拉力。在地球表面，这些力量导致两个板块相互滑动（板块边界）的地震。下沉板块的力有效地将构造板块拉到身后的能力取决于板块在地幔内的变形方式，而这又取决于板块变形时其材料特性如何变化。此外，与下沉板块相关的总力取决于矿物晶体结构的变化（相变），这导致板块内密度的变化。 这些相变大多发生在地表以下410到660公里处，这一区域被称为过渡带。最后，地幔内部下沉板块的变形表现在板块内部至地球表面以下660公里深处的地震活动，以及地球表面板块运动的可观测变化。本研究的目的是确定，1）表面板块运动和表面板块内的应力状态如何对过渡中的板块动力学做出反应并提供反馈，2）深板块地震活动的起源是什么，以及3）如果观察到的板块形状与俯冲板块和板块边界的内在属性有关，或者是板的时间相关演化的反映。而这项研究的重点是在地球内部的变形？为了解决这些问题，我们将开发俯冲动力学的三维数值模型（模拟）。更具体地说，我们将使用最好的实验室和观测约束的矿物组成的板块（地壳，残留hazburzburgery和地幔层），相变（包括所有主要的矿物成分）和流变学的板块和地幔。我们将使动态移动的板块和板块边界，这是必不可少的了解板变形和表面板块运动之间的物理联系。这些模型消除了以前研究中使用的几个简化假设，使我们能够在板变形和表面板块运动以及板地震活动之间建立联系。将把模型结果与关于板块形状、板块特征和运动学的全球数据集，以及关于板块内应力状态的区域地震观测和整个俯冲岩石圈的地震不连续性（发生在相变时）进行比较。这个项目的结果将提供一个更完整和现实的理解，控制板的变形和他们的能力，拉构造板块的物理过程，并深入了解板地震活动是如何与更大规模的变形板。此外，该研究将支持博士生的培训，为建模社区贡献软件，向本科生介绍科学研究，并为本科教学中使用的材料做出贡献。