Evolution and dynamics of subduction, plumes and plate motions

俯冲、羽流和板块运动的演化和动力学

• 批准号: 1247022
• 负责人: Michael Gurnis
• 金额: $ 56万
• 依托单位: California Institute of Technology
• 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 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1247022&HistoricalAwards=false
• 关键词: Evolution; dynamics; subduction; plumes; plate

The surface of the earth is in constant motion via a process known as plate tectonics. The surface of the earth is divided into about a dozen tectonic plates whereby one plate moves (at a few inches per year) with respect to other plates along great faults and fault zones. Although these motions seem small, they are responsible for earthquakes, including great earthquakes, mountain building, and the formation of sedimentary basins. Consequently, plate tectonics is simultaneously responsible for both some of the most significant geological hazards as well as the formation of the largest hydrocarbon reservoirs. With this project, we aim to better understand the forces that drive and resist plate motions and thereby obtain a deeper understanding of the forces that drive natural hazards and natural resources. Within this project, by linking the most advanced computational tools to existing observations, we will determine the forces and physical properties associated with plate tectonics. The most important impact will be the training of two Ph.D. students in geophysics and a postdoctoral scholar. They will gain enormous experience with sophisticated numerical methods, supercomputing technologies, and the linkage of data with numerical models. These are essential skills in science and the new knowledge economy. The proposed research will impact several large observational programs by developing hypotheses that could be tested with deep sea drilling under the auspices of IODP and geological sampling and seismic imaging of the Aleutian Island chain under the GeoPRISM project.We propose to test hypotheses for changes in the plate tectonic system with a new generation of geodynamic models and bring new observational constraints to bear on the dynamics of plate motions. We will focus on changes in plate speed & direction and formation of new subduction zones because the observations will allow us to constrain uncertain mantle and lithospheric properties. Specifically, plate motions are likely strongly resisted by bending of the slab in a subduction zone, a force that depends on lithospheric viscosity, but this viscosity remains poorly known and we propose to place tighter bounds on it and other uncertain properties by matching observations in the time domain -- in much the same way that a combination of time-dependent and present day observations of post-glacial rebound are used to constrain the background mantle viscosity. First, we will use generic, fully dynamic 3D models to self-consistently explore the balance between changes in plate motions and changes to subduction and plumes. Second, we will use realistic models to better establish the link between dynamics and detailed geological and geochemical observations of specific examples of subduction initiation. Third, we will build detailed structural models of the mantle and lithosphere in the geological past using an approach that assimilates plate tectonic reconstructions into models of mantle convection along with inverse methods that allow estimation of initial conditions, density anomalies, and viscosity structures. Through these three approaches, we aim to more fully establish the dynamic link between changing plate motions and how they translate into and result from changes in subduction, with specific linkages to geophysical and geological observations. The models will be high resolution (e.g. locally 1 km or less where needed) and fully incorporate the extreme variations in viscosity between the slab and mantle, hinge zone and interface between subducting and over-riding plates.

地球表面通过一个被称为板块构造的过程不断运动。地球表面被划分为十几个构造板块，其中一个板块相对于其他板块沿着大断层和断层带移动（每年几英寸）。虽然这些运动看起来很小，但它们是地震的原因，包括大地震，造山运动和沉积盆地的形成。因此，板块构造是同时负责一些最重要的地质灾害，以及最大的油气藏的形成。通过这个项目，我们的目标是更好地了解驱动和抵抗板块运动的力量，从而更深入地了解驱动自然灾害和自然资源的力量。在这个项目中，通过将最先进的计算工具与现有的观测相结合，我们将确定与板块构造相关的力和物理特性。最重要的影响将是培养两名博士。他是一名物理学专业的学生和一名博士后学者。他们将获得丰富的经验，复杂的数值方法，超级计算技术，以及数据与数值模型的联系。这些都是科学和新知识经济的基本技能。拟议的研究将影响几个大型观测项目，通过发展假设，可以测试的深海钻探的主持下，IODP和地质采样和地震成像的阿留申群岛链下的GeoPRISM项目。我们建议测试假设的板块构造系统的变化与新一代的地球动力学模型，并带来新的观测约束，以承担板块运动的动力学。我们将把重点放在板块速度方向的变化和新的俯冲带的形成，因为观测将使我们能够限制不确定的地幔和岩石圈性质。具体来说，板块运动可能受到俯冲带板块弯曲的强烈抵抗，这种力取决于岩石圈粘性，但这种粘性仍然知之甚少，我们建议通过在时域中匹配观测值来对它和其他不确定的性质设置更严格的界限--以与时间相关的和当今后现代观测相结合的方式，冰川反弹被用来约束背景地幔粘度。首先，我们将使用通用的、完全动态的3D模型来自洽地探索板块运动变化与俯冲和地幔柱变化之间的平衡。第二，我们将使用现实的模型，以更好地建立动力学和详细的地质和地球化学观测的具体例子的俯冲开始之间的联系。第三，我们将建立详细的结构模型的地幔和岩石圈在过去的地质使用的方法，同化板块构造重建到地幔对流模型沿着与逆方法，允许估计的初始条件，密度异常，和粘度结构。通过这三种方法，我们的目标是更充分地建立不断变化的板块运动之间的动态联系，以及它们如何转化为俯冲的变化并由此产生，并与地球物理和地质观测有具体的联系。这些模型将是高分辨率的（例如，在需要时局部分辨率为1公里或更低），并充分考虑到板块和地幔之间、铰链区以及俯冲板块和上覆板块之间的界面之间粘度的极端变化。