CAREER: When Subduction Fails - Dynamical Models of Oceanic Plateau Collision and Crustal-Fragment Accretion

职业：当俯冲失败时——海洋高原碰撞和地壳碎片吸积的动力学模型

• 批准号: 0748818
• 负责人: Magali Billen
• 金额: $ 48.83万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-01-01 至 2013-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0748818&HistoricalAwards=false
• 关键词: CAREER; When; Subduction; Fails; Dynamical

Most studies of subduction dynamics attempt to determine the processes responsible for sustaining long-term subduction of typical oceanic lithosphere. While active subducting slabs have seismicity evident of intense internal deformation to various depths, the slab continues to directly transmit stresses to the surface plate. Only under special conditions does the slab become sufficiently weak or the positive buoyancy of the surface plate sufficiently large to cause subduction to fail. By looking at cases when subduction fails we can learn about the processes required to sustain longterm subduction. Three-dimensional thermo-mechanical models are being used to address two processes of subduction failure: 1) How does attempted oceanic plateau subduction cause subduction to fail? 2) How does crustal-fragment loss occur during normal subduction? These studies focus on the first-order, essential processes, such as the basic rheologic layering of the oceanic plate and localization processes, phase transformations that change rheology and/or density, the size and geometry of structures, and obliquity of convergence. The educational components of this project build directly on the research objectives, by using the dynamical model results as synthetic data sets to help students master 3D spatial thinking skills. Laboratory and homework exercises are being developed from the numerical model results that ask students to create a cross section of the subsurface structure from mapped data of structure orientations (strike, dip) taken from the synthetic 3D models. This part of the exercise simulates the interpretive exercise students normally carry out with actual mapped data taken in the field. However, unlike the field experience, the students are then given the opportunity to correct their initial cross section after exploring the actual 3D structure using visualization software, which allows them to create cross sections of any orientation and view the 3D structures as isosurfaces. In addition, a new feature is being added to the visualization software that allows the surface of the 3D numerical data to be sliced with any pre-defined 2D topographic surface (instead of a simple plane). This tool allows students to explore directly how topography influences the surface outcrop of 3D subsurface structures (e.g., intersection of a dipping fault with a valley versus a ridge).

俯冲动力学的大多数研究试图确定负责维持典型海洋岩石圈长期俯冲的过程。虽然主动俯冲平板具有明显的强烈内部变形的地震性，但平板继续直接将应力直接传输到表面板。只有在特殊条件下，平板才变得足够弱或表面板的正浮力足以使俯冲失败。通过查看俯冲失败的案例，我们可以了解维持长期俯冲所需的过程。三维热机械模型被用于解决两个俯冲失败的过程：1）尝试的海洋高原俯冲俯冲如何导致俯冲失败？ 2）在正常俯冲期间如何发生地壳碎片损失？这些研究集中于一阶，必不可少的过程，例如海洋板和定位过程的基本流变分层，改变流变学和/或密度的相变，结构的大小和几何形状以及收敛的倾斜度。该项目的教育组成部分直接基于研究目标，它通过使用动态模型结果作为综合数据集来帮助学生掌握3D空间思维技能。实验室和家庭作业练习是根据数值模型结果开发的，该结果要求学生从合成3D模型中获取的结构取向的映射数据（打击，倾斜）中创建地下结构的横截面。练习的这一部分模拟了解释性练习学生通常在现场获取的实际映射数据。但是，与现场体验不同，在使用可视化软件探索实际的3D结构后，让学生有机会纠正其初始横截面，这使他们可以创建任何方向的横截面，并将3D结构视为Isosurfaces。此外，正在将新功能添加到可视化软件中，该功能允许使用任何预定的2D地形表面（而不是简单的平面）切成3D数值数据的表面。该工具允许学生直接探索地形如何影响3D地下结构的表面露头（例如，与山谷与山脊相交的浸入故障的交点）。