Collaborative Research: The Asthenosphere and Mantle Dynamics

合作研究：软流圈和地幔动力学

• 批准号: 0944229
• 负责人: Mark Richards
• 金额: $ 5.66万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-04-01 至 2014-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0944229&HistoricalAwards=false
• 关键词: Collaborative; Research; Asthenosphere; Mantle; Dynamics

The theory of plate tectonics is one of the great intellectual revolutions of the past 50 years. The theory remains a kinematic one in that it does not self-consistently address the connection between plate motions and the Earth's internal energy sources which must, in some way, be the drivers of plate motion. Extending plate tectonics to a fully dynamic theory is a fundamental current challenge in Earth science. The motivations for doing so go beyond studies of the Earth's interior as the operation of plate tectonics has implications for long term climate history and for the evolution of life on our planet. Although it is agreed that the convective cooling of the Earth's interior is associated with plate motions, the specifics of the connection are not fully understood. Our work will make a vital step in closing the loop, so to speak, by elucidating the dynamics and feedback mechanisms associated with plate tectonics and convection in the Earth's mantle. It has long been suspected that a region of low relative strength beneath tectonic plates, i.e., the asthenosphere, plays a fundamental role in connecting plate motions to convection in the Earth's interior. We will quantify this idea through a combination of data analysis and state of the art numerical modeling. By comparing our modeling predictions to observations we will be able to test the hypothesis that plate tectonics depends on the presence of a low viscosity asthenosphere. If correct, this will have implications beyond a better understanding of our own planet (e.g., Venus lacks evidence for an asthenosphere and for currently active plate tectonics). We will perform 3D spherical mantle convection simulations to explore the combined effects of a low-viscosity asthenosphere and plate boundary failure, at parameter values appropriate to Earth's mantle. We will augment our numerical work with theoretical scaling analysis to keep interpretations of the numerical work on a solid footing, and to predict model behavior in previously unexplored regimes. Our analysis will provide insight into model dynamics in terms of energetic balances between the resistance to plate motion associated with dissipation at plate margins, within the asthenosphere, and in the bulk mantle. This will allow us to link our dynamic modeling to instantaneous flow studies that isolate the balance of dissipation between plate processes and the bulk mantle. This linkage will bring added observational constraints to bear on our numerical simulations. Our modeling will also make predictions regarding plate size distribution, plate velocities, heat flow, dynamic topography, gravity signals, the power spectrum of mantle thermal anomalies, and seismic anisotropy to be compared (statistically) with observations. The combination of simulations, physical analysis, and data constraints will provide insight into the geologically recent dynamics of the solid Earth. With this in hand, our analysis and modeling will be extended to address the role of the asthenosphere for the thermal history of our planet.

板块构造理论是过去50年来最伟大的知识革命之一。该理论仍然是一个运动学的，因为它没有自洽地解决板块运动和地球内部能源之间的联系，在某种程度上，必须是板块运动的驱动力。将板块构造扩展为完全动力学理论是地球科学当前的一个基本挑战。这样做的动机超出了地球内部的研究，因为板块构造的运作对长期气候历史和地球上生命的进化有影响。虽然人们一致认为地球内部的对流冷却与板块运动有关，但这种联系的细节还没有完全理解。可以说，我们的工作将通过阐明与板块构造和地幔对流有关的动力学和反馈机制，在闭合循环方面迈出重要的一步。长期以来，人们一直怀疑构造板块之下的相对强度较低的区域，即，软流层在连接板块运动和地球内部对流方面起着重要作用。我们将通过数据分析和最先进的数值建模相结合来量化这一想法。通过比较我们的模型预测的观测，我们将能够测试的假设，板块构造取决于低粘度软流圈的存在。如果是正确的，这将产生超越更好地了解我们自己的星球的影响（例如，金星缺乏软流层和当前活跃板块构造的证据）。我们将进行三维球形地幔对流模拟，以探讨低粘度软流圈和板块边界故障的综合影响，在参数值适合地球的地幔。我们将用理论尺度分析来增强我们的数值工作，以保持对数值工作的解释有一个坚实的基础，并预测以前未探索过的机制中的模型行为。我们的分析将提供洞察模型动力学的能量平衡之间的阻力与耗散在板块边缘，软流圈内，并在散装地幔板块运动。这将使我们能够将我们的动态建模与瞬时流动研究联系起来，这些研究隔离了板块过程和大块地幔之间的耗散平衡。这种联系将给我们的数值模拟带来额外的观测约束。我们的模型还将对板块尺寸分布、板块速度、热流、动态地形、重力信号、地幔热异常的功率谱和地震各向异性进行预测，并与观测结果进行比较（统计学）。模拟，物理分析和数据约束的结合将提供对固体地球地质学最新动态的洞察。有了这一点，我们的分析和建模将扩展到解决我们星球的热历史的软流层的作用。