Collaborative Research: Relating Bulk Composition to Seismic Properties in Crustal Rocks

合作研究：将地壳岩石的块体成分与地震特性联系起来

• 批准号: 1722935
• 负责人: Oliver Jagoutz
• 金额: $ 30.5万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-07-15 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1722935&HistoricalAwards=false
• 关键词: Collaborative; Research; Relating; Bulk; Composition; Collaborative; Research; Relating; Bulk; Composition

The Earth's continental crust is a reservoir for minerals and other natural resources. Moreover, the chemical composition of the crust controls its material properties (e.g., strength), and thus influences the way in which the crust deforms and evolves over geologic time. However, while crustal composition at the Earth?s surface can be determined by direct sampling, at depth composition must be inferred from indirect methods such as geophysical imaging. One of the most common geophysical imaging methods employs seismic waves, which travel at different speeds through different rock types. By measuring seismic wave speeds the 3-D internal structure of the crust can be determined using an approach similar to x-ray computed tomography (CT scan) in medical studies. In this project, we will take seismic velocity models for the Earth?s continental crust and invert them to infer crustal composition. These compositional models will then be used to determine variations in crustal strength, as well as regions with different natural resource potential.In the past decades a wealth of seismic data characterizing the continental crust have become available through NSF programs such as Earthscope, GeoPRISMS, and the Cascadia Initiative?including co-located P-wave data from controlled-source experiments, VP/VS constraints from receiver functions, and S-wave data from ambient noise tomography. These datasets provide the foundation for future research on the nature and composition of the continental crust. However, despite the abundance of information provided by the seismic data, a quantitative relationship between rock composition and seismic velocity is missing. In this project we will develop a new suite of tools to relate crustal composition to seismic velocity. Our approach is divided into four steps: (1) derive a representative database for crustal composition space, (2) perform thermodynamic calculations of the equilibrating mineral assemblages for each composition at various equilibrium P,T, H2O and fO2 conditions, (3) calculate VP and VS for each phase assemblage for different in situ P,T conditions, and (4) use the resulting dataset to establish forward relationships between crustal composition and seismic velocity. These data will be compiled into a publically available online database, which can be used by others to derive relationships between major element chemistry and seismic velocity under a specified range of crustal conditions. The project will support MIT/WHOI Joint Program student William Shinevar. To maximize the utility of the compositional inversion to the community we will develop a web-based Java applet to allow users to directly invert major element compositions from their own seismic datasets.

地球的大陆壳是矿物质和其他自然资源的储藏室。此外，地壳的化学组成控制其材料特性（例如强度），从而影响地壳在地质时代的变形和发展的方式。但是，尽管可以通过直接采样来确定地球表面的地壳组成，但必须从间接方法（例如地球物理成像）中推断出在深度组成下。最常见的地球物理成像方法之一采用地震波，以不同的速度通过不同的岩石类型传播。通过测量地震波速度，可以使用类似于医学研究中类似于X射线计算机断层扫描（CT扫描）的方法来确定地壳的3-D内部结构。在这个项目中，我们将对地球的大陆地壳进行地震速度模型，并倒转它们以推断地壳成分。 These compositional models will then be used to determine variations in crustal strength, as well as regions with different natural resource potential.In the past decades a wealth of seismic data characterizing the continental crust have become available through NSF programs such as Earthscope, GeoPRISMS, and the Cascadia Initiative?including co-located P-wave data from controlled-source experiments, VP/VS constraints from receiver functions, and S-wave data from环境噪声断层扫描。这些数据集为未来研究大陆地壳的性质和组成的研究奠定了基础。然而，尽管地震数据提供了大量信息，但岩石组成与地震速度之间的定量关系仍缺少。在这个项目中，我们将开发一套新的工具，将地壳组成与地震速度联系起来。我们的方法分为四个步骤：（1）在地壳组成空间中得出一个代表性数据库，（2）对每个均衡的平衡矿物组合进行热力学计算，以在各种平衡的情况下，t，h2o和fo2条件下的各种平衡情况下，（3）计算各个阶段的vp和vs的情况，以对不同的情况进行cro依次，并在上述情况下（4）在t的情况下（4）在t creption中，（4）组成和地震速度。这些数据将被编译为公开可用的在线数据库，在指定的地壳条件范围内，其他人可以使用该数据来得出主要元素化学和地震速度之间的关系。该项目将支持MIT/WHOI联合计划的学生William Shinevar。为了最大化构图反转到社区的效用，我们将开发一个基于Web的Java小程序，以允许用户直接从其自己的地震数据集中反转主要元素构图。