CSEDI Collaborative Research: Influence of Grain-Size Evolution on Global and Regional Mantle Flow and Upper Mantle Seismic Structure

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的，尽管地球上的大规模对流？尽管地幔最终控制着地球表面的构造变形，但深层地幔流动与板块构造之间的联系仍然知之甚少。这是因为地幔流动的模式很难从地面观测中得到约束，并且对控制板块-地幔耦合带（即软流圈）内岩石变形的物质（或流变）特性的变化很敏感。该项目的目标是利用计算机模拟来评估地球的物质特性如何影响地幔对流的类型。这种理解很重要，因为它将帮助我们量化控制地质变形及其相关地震危险的构造力，特别是在大多数大地震和火山爆发发生的板块边界。该项目的结果将直接与nsf赞助的几个项目相关，如边际、Ridge2000、CSEDI、CIG和Earthscope，并将帮助资助WHOI和夏威夷大学的研究生。在地球上？在软流圈中，地幔流变取决于温度、压力、含水量、变形模式和粒度等多种因素，而这些因素都取决于地幔流动的时变演化。在这个项目中，研究人员将在区域（10到100公里）和全球（100到1000公里）的三维地幔流动模型中，通过计算微观尺度（厘米或更小）的粒度演化来研究地幔流变学的粒度依赖性。他们将通过将基于实验室的粒度演化模型整合到大规模地幔流动模型中来研究粒度、岩石流变和流动之间反馈的潜在重要性，从而实现这一目标。这些数值模型的预测将受到地震数据（包括地震各向异性、波速和衰减的变化）和构造环境谱中岩石结构分析的约束。在此过程中，他们将提高我们对地幔流动、地表构造和上地幔颗粒大小之间关系的理解。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5) Although large-scale convection in the Earth?s mantle ultimately controls tectonic deformation at the Earth's surface, the link between deep mantle flow and plate tectonics remains poorly understood. This is because patterns of mantle flow are difficult to constrain from surface observations and are sensitive to variations in the material (or rheologic) properties that control rock deformation within the plate-mantle coupling zone known as the asthenosphere. The goal of this project is to use computer simulations to evaluate how the material properties of the Earth influence the style of mantle convection. This understanding is important because it will help us quantify the tectonic forces that control geologic deformation and its associated seismic hazard, particularly at plate boundaries where most major earthquakes and volcanic eruptions occur. The results of this project will be directly relevant to several NSF-sponsored programs such as Margins, Ridge2000, CSEDI, CIG, and Earthscope and will help fund graduate students at both WHOI and the University of Hawaii. In the Earth?s asthenosphere, mantle rheology depends on a variety of factors including temperature, pressure, water content, deformation mode, and grain-size, all of which depend on the time-dependent evolution of mantle flow. In this project, the investigators will examine the grain-size dependence of mantle rheology by computing grain-size evolution on a micro-scale (cm and smaller) within 3-D mantle flow models on regional (10s to 100s km) and global (100s to 1000s km) scales. They will accomplish this by incorporating laboratory-based models for grain-size evolution into large-scale mantle flow models to investigate the potential importance of feedbacks between grain-size, rock rheology, and flow. The predictions made by these numerical models will be constrained using seismic data (including variations in seismic anisotropy, wave speed, and attenuation) and rock texture analyses from a spectrum of tectonic environments. In doing so, they will improve our understanding of the relationship between mantle flow, surface tectonics, and grain size in the upper mantle.