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

该奖项由 2009 年美国复苏和再投资法案（公法 111-5）资助。尽管地幔中的大规模对流最终控制了地球表面的构造变形，但深层地幔流和板块构造之间的联系仍然知之甚少。这是因为地幔流的模式很难受到表面观测的限制，并且对控制板-地幔耦合区（称为软流圈）内岩石变形的材料（或流变）特性的变化敏感。该项目的目标是使用计算机模拟来评估地球的材料特性如何影响地幔对流的方式。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灾害的构造力，特别是在大多数重大地震和火山爆发发生的板块边界处。该项目的结果将与几个 NSF 资助的项目直接相关，例如 Margins、Ridge2000、CSEDI、CIG 和 Earthscope，并将帮助资助 WHOI 和夏威夷大学的研究生。在地球的软流圈中，地幔流变取决于多种因素，包括温度、压力、含水量、变形模式和颗粒尺寸，所有这些都取决于地幔流随时间的演化。在该项目中，研究人员将通过在区域（10 到 100 公里）和全球（100 到 1000 公里）尺度的 3D 地幔流模型中计算微观尺度（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纳入大规模地幔流模型中，以研究粒度、岩石流变学和流动之间的反馈的潜在重要性来实现这一目标。这些数值模型所做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）和来自一系列构造环境的岩石纹理分析的约束。这样做将增进我们对地幔流、地表构造和上地幔颗粒尺寸之间关系的理解。

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.