Integrated Analytical-Computational Analysis of Microstructural Influences on Seismic Anisotropy

微观结构对地震各向异性影响的综合解析计算分析

• 批准号: 1118786
• 负责人: Scott Johnson
• 金额: $ 29.82万
• 依托单位: University of Maine
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-08-15 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1118786&HistoricalAwards=false
• 关键词: Integrated; Analytical; Computational; Analysis; Microstructural

The magnitudes, orientations and spatial distributions of elastic anisotropy in Earth?s crust and mantle carry valuable information about gradients in thermal, mechanical and kinematic parameters arising from mantle convection, mantle-crust coupling and tectonic plate interactions. Relating seismic signals to deformation regimes requires knowledge of the elastic signatures (bulk stiffnesses) of different microstructures that characterize specific deformation environments, but the influence of microstructural heterogeneity on bulk stiffness has not been comprehensively evaluated. The objectives of this project are to: (1) scale up a preliminary method to determine the bulk stiffness of rocks using integrated analytical (electron backscatter diffraction) and computational (asymptotic expansion homogenization) approaches that fully account for the grain-scale elastic interactions among the different minerals in the sample; (2) apply this integrated framework to investigate the effect on elastic anisotropy of several common crustal microstructures; (3) integrate time-dependent microstructure modeling with bulk stiffness calculations to investigate the effects of strain- and process-dependent microstructure evolution on elastic anisotropy in mantle rocks; and (4) disseminate open-source software for the calculation of bulk stiffnesses from electron backscatter diffraction data and creation of synthetic (computer generated) microstructures that can be used in sensitivity analyses among other applications. Because commonly used methods, such as the Voigt, Reuss and Voigt-Reuss-Hill averages, for calculating bulk rock stiffnesses do not account for elastic interactions among the constituent minerals, they exhibit marked, non-systematic differences from stiffnesses obtained using asymptotic expansion homogenization.These objectives are important because the results would substantially improve understanding of the nature of seismic anisotropy in the Earth's crust, which is composed of rocks dominated by low symmetry minerals with complex structures. Traditional methods for performing these calculations do not easily incorporate these effects. This project will develop an elegant, easily-implemented alternative method for anisotropic materials. The scientific results and computational tools that result from this project will have global application across a number of solid Earth and engineering disciplines. Open-source codes developed in this project will made available through existing open-source ELLE platform. Classroom exercises developed for Earth Science and Mechanical Engineering courses that employ this software will be make available to the community, probably through the Science Education Resource Center website at Carleton College.

地壳和地幔中弹性各向异性的幅度，方向和空间分布具有有关厚，机械和运动学参数梯度的有价值信息，这是由地幔对流，地幔壳耦合和构造板块相互作用引起的。将地震信号与变形方案相关联需要了解表征特定变形环境的不同微观结构的弹性特征（散装刚度），但是尚未对微结构异质性对块状刚度的影响进行全面评估。该项目的目标是：（1）扩展一种初步方法，以使用集成分析（电子反向散射衍射）和计算（渐近扩张均化均化）方法来确定岩石的块状刚度，以完全说明样品中不同矿物质之间的晶尺度弹性相互作用； （2）应用此集成框架来研究对几种常见的地壳微观结构的弹性各向异性的影响； （3）将时间依赖性的微观结构建模与块状刚度计算相结合，以研究应变和过程依赖性微观结构演变对地幔岩石中弹性各向异性的影响； （4）传播开源软件，用于计算电子反向散射数据的散装刚度，并创建合成（计算机生成的）微结构，这些微结构可用于敏感性分析。因为常见的方法，例如voigt，reuss和voigt-russ-hill平均，用于计算散装岩石刚度并不能说明成分矿物质之间的弹性相互作用，因此它们表现出明显的，非系统的差异，从而使用异性范围来改善了既定的，因为该较高的质量是重要的。地壳，由岩石组成，由具有复杂结构的低对称矿物支配。执行这些计算的传统方法不容易纳入这些效果。该项目将开发一种针对各向异性材料的优雅，易于实现的替代方法。该项目产生的科学结果和计算工具将在许多固体地球和工程学科中具有全球应用。该项目中开发的开源代码将通过现有的开源Elle平台提供。为地球科学和机械工程课程开发的课堂练习可能会通过Carleton College的科学教育资源中心网站提供给社区。

项目成果

Pervasive cracking of heterogeneous brittle materials using a multi-directional smeared crack band model

• DOI: 10.1016/j.ijmecsci.2017.09.016
• 发表时间: 2017-09
• 期刊: International Journal of Mechanical Sciences
• 影响因子: 7.3
• 作者: A. C. Cook;S. Vel;S. E. Johnson

Modification of crustal seismic anisotropy by geological structures (“structural geometric anisotropy”)

• DOI: 10.1130/ges01655.1
• 发表时间: 2019-02
• 期刊: Geosphere
• 影响因子: 2.5
• 作者: D. Okaya;S. Vel;W. Song;S. E. Johnson