Collaborative Research: A Study of Deep Subduction Integrating Broadband Seismology and Mineral Physics

合作研究：宽带地震学与矿物物理学相结合的深俯冲带研究

• 批准号: 0552011
• 负责人: Harry Green
• 金额: $ 32.5万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-07-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0552011&HistoricalAwards=false
• 关键词: Collaborative; Research; Study; Deep; Subduction

The discovery of plate tectonics has focused attention to the dynamic nature of the Earth's interior. One of the first-order issues is the interaction between subducted plates and the transition zone of the mantle, a key layer at 410-660 km depth that divides the upper and lower mantle. In particular, the amount of plate material that descends into the lower mantle is central to understanding thermal convection and chemical mixing of the Earth's interior. While studies have suggested that subducted plates generally penetrate deep into the lower mantle, a number of recent results from experimental rock mechanics, computer simulations, and focused seismic observations all suggest that cold, rapidly subducting plates may become buoyant in the mantle transition zone due to the presence of important compositional components. A new collaborative study by researchers from 5 different institutions is seeking to understand what is really happening to plates as they travel down into the Earth. To answer these fundamental questions, the researchers are focusing on two key issues affecting the fate of plates: 1) The nature of a key boundary in the Earth's interior (660-km discontinuity), including its topography and density contrast near subduction zones; 2) how changes in rock type and density associated with deep earthquakes appear to mark pieces of plate that stagnated on their downward descent, particularly for plates driven down into the earth quickly. This project is investigating these questions by incorporating data from nature, the experimental laboratory, and computer simulations. The natural laboratories being examined are the deep subduction zones along the western Pacific, where old, cold plate has been rapidly subducting for millions of years. These areas provide an exceptional environment to examine what happens to subducting plates deep within the Earth. Seismologists are studying the subducted plates using the precise distribution of deep earthquakes, their faulting patterns, and the properties of the seismic waves in the rocks that surround them. For the experimental component, the mineral physics laboratory is investigating how seismic observations can be explained by patterns and alignment of crystals within different rock types from great depth in the Earth. Researchers are also examining whether plates become weak as they travel down into the Earth's interior by looking at how rocks behave when they are subjected to intense pressure and heat. To place the natural and experimental results in proper context, advanced computer simulations of plate subduction are investigating the geodynamic effects of changes in properties like composition, temperature, density, and viscosity. This project is providing training for three graduate students per year, and the collaborative nature of the work ensures that their training will be significantly enriched and broadened. In addition to the broad context of the interdisciplinary research, there is a component of education and outreach for the general audience. An animated teaching module is being created with help from the Educational Multimedia Visualization Center in order to illustrate various scenarios of plate subduction, focusing on the plate interaction with the mantle transition zone.

板块构造的发现引起了人们对地球内部动态性质的关注。 其中一个首要问题是俯冲板块与地幔过渡带之间的相互作用，地幔过渡带是位于 410-660 公里深度、分隔上地幔和下地幔的关键层。 特别是，下降到下地幔的板块材料的数量对于理解地球内部的热对流和化学混合至关重要。 虽然研究表明俯冲板块通常会深入到下地幔中，但最近来自实验岩石力学、计算机模拟和集中地震观测的大量结果都表明，由于重要成分成分的存在，寒冷、快速俯冲的板块可能会在地幔过渡带中变得浮力。 来自 5 个不同机构的研究人员进行了一项新的合作研究，旨在了解板块在进入地球时到底发生了什么。 为了回答这些基本问题，研究人员正在关注影响板块命运的两个关键问题：1）地球内部关键边界（660公里的不连续性）的性质，包括俯冲带附近的地形和密度对比； 2）与深部地震相关的岩石类型和密度的变化如何似乎标志着在向下下降过程中停滞的板块，特别是对于快速沉入地球的板块。 该项目正在通过结合来自自然、实验实验室和计算机模拟的数据来研究这些问题。 正在检查的自然实验室是西太平洋沿岸的深俯冲带，那里古老的冷板块已经快速俯冲了数百万年。 这些地区提供了一个特殊的环境来研究地球深处俯冲板块的情况。 地震学家正在利用深部地震的精确分布、断层模式以及周围岩石中地震波的特性来研究俯冲板块。 对于实验部分，矿物物理实验室正在研究如何通过地球深处不同岩石类型内晶体的模式和排列来解释地震观测。 研究人员还通过观察岩石在承受强烈压力和热量时的行为来检查板块在进入地球内部时是否会变弱。 为了将自然和实验结果置于适当的背景下，板块俯冲的先进计算机模拟正在研究成分、温度、密度和粘度等特性变化的地球动力学效应。 该项目每年为三名研究生提供培训，工作的协作性质确保了他们的培训将得到显着丰富和拓宽。 除了跨学科研究的广泛背景之外，还有针对普通受众的教育和宣传的组成部分。在教育多媒体可视化中心的帮助下，正在创建一个动画教学模块，以说明板块俯冲的各种场景，重点关注板块与地幔过渡带的相互作用。