Untangling the Roles of Viscous, Elastic, and Plastic Deformation in Slab Bending

阐明粘性变形、弹性变形和塑性变形在板坯弯曲中的作用

• 批准号: 2054597
• 负责人: Ikuko Wada
• 金额: $ 16.07万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-03-01 至 2025-02-28
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2054597&HistoricalAwards=false
• 关键词: Untangling; Roles; Viscous; Elastic; Plastic

Sinking of a tectonic plate beneath another plate into the mantle is called subduction. It is a fundamental process that controls the evolution of Earth and holds a key to understanding important processes, such as earthquakes, volcanism, and mantle convection. However, how subduction initiates and how the tectonic plate changes its shape during subduction initiation (SI) are still unclear. The key driving forces are the negative buoyancy of the subducting plate and external forces that push the tectonic plates laterally. The key resisting forces include bending resistance of the subducting plate, frictional resistance between the subducting and overriding plates, and viscous resistance that is exerted by the surrounding mantle on the subducting plate. The details of SI and how the subducting plate bends depend strongly on the balance between these forces and also on the strength of the subducting slab, which has been defined by some combination of viscosity, elasticity, and plasticity of Earth materials. Further, these material prosperities are often assumed to be uniform in numerical simulations of SI despite their dependence on pressure, temperature, stress, and composition. Which of the three mechanical properties (i.e., viscosity, elasticity, and plasticity) controls the bending of the subducting plate depends on their relative values. Using numerical models, this study aims to better understand how the bending behavior of the subducting plate changes with the three mechanical properties. The project provides support for an early-career female faculty member and a postdoctoral scholar.A suite of generic 2-D and 3-D dynamic subduction models with a visco-plastic and a visco-elasto-plastic rheology will be developed to quantify the effect of elasticity on down-dip and lateral bending of the subducting slab. These models will incorporate a composite viscous rheology that accounts for both dislocation creep and diffusion creep, and models with the visco-elasto-plastic rheology incorporates pressure- and temperature-dependent shear modulus, using the thermodynamic code Perple_X. The models are used to address two key questions: (1) Can the negative buoyancy of the oceanic lithosphere be sufficient to overcome the elastic bending resistance and to initiate subduction, and (2) Is elasticity a rheological component that resists or facilitates down-dip and lateral bending/unbending? Systematic tests on the effect of subduction parameters on the slab evolution will also be performed to address these questions. Further, 2-D and 3-D models will be developed for selected real subduction systems, including Marianas, Tonga, and Puysegur, and the results will be compared with the tectonic history and the current slab geometry. The numerical models to be developed will provide not only the geometrical evolution of the slab but also the temperature and mantle flow fields of subduction systems over a range of parameters, and the information will be useful for the interpretations of geophysical and geochemical observations. The results will be summarized in scientific videos to be distributed through the PI’s research website and YouTube as well as in conference presentations and peer-reviewed journal articles.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

在另一盘板下的构造板沉入地幔中称为俯冲。这是一个控制地球演变的基本过程，并拥有理解重要过程的关键，例如地震，火山主义和地幔转换。然而，俯冲如何启动以及构造板在俯冲计划（SI）期间如何改变其形状。仍然尚不清楚。关键的驱动力是俯冲板的负浮力和外部力的外部力，它们横向推动构造板。钥匙阻力包括俯冲板的弯曲电阻，俯冲和压倒板之间的摩擦电阻以及由俯冲板上周围地幔执行的粘性电阻。 Si的细节以及俯冲板弯曲如何在这些力之间以及俯冲板之间的强度上依赖于粘度，弹性和地球材料的可塑性的某种结合来定义。此外，通常认为这些物质繁荣在SI目的地的数值模拟中是统一的，它们对压力，温度，压力和组成的依赖。三种机械性能（即粘度，弹性和可塑性）中的哪个控制俯冲板的弯曲取决于它们的相对值。使用数值模型，本研究旨在更好地了解俯冲板的弯曲行为如何随三个机械性能而变化。该项目为早期的女性教师和博士后科学提供了支持。将开发出具有粘性塑料和Visco-elasto塑性流变学的通用2-D和3-D动态俯冲模型的套件，以量化弹性对弹性Slab的下向上弯曲的效果。这些模型将结合一种复合粘性流变性，该粘稠流变性既说出位错蠕变又是扩散蠕变，并且使用热力学代码PERPERPERPLE_X，具有Visco-Elasto-Plasto-Plastic Rheology的模型结合了压力和温度依赖性的剪切模量。模型用于解决两个关键问题：（1）海洋岩石圈的负浮力是否足以克服弹性弯曲抗性并启动俯冲，并且（2）是弹性的流变学成分，一种抗拒或促进下倾和侧向和侧向弯曲/不弯曲/不弯曲/避免的流变学成分？还将对俯冲参数对平板演化的影响进行系统测试，以解决这些问题。此外，将为选定的实际俯冲系统（包括Marianas，Tonga和Puysegur）开发2-D和3-D模型，结果将与构造历史和当前的板几何形状进行比较。要开发的数值模型不仅可以提供平板的几何演化，而且还提供了一系列参数的俯冲系统的温度和地幔流场，并且该信息将有助于解释地球物理和地球化学观测。该结果将在科学视频中汇总，将通过PI的研究网站和YouTube以及会议演讲和同行评审的期刊文章进行分发。该奖项反映了NSF的法定任务，并被认为是通过基金会的知识分子优点和更广泛的影响审查标准来通过评估来通过评估来获得的支持。

项目成果

Effects of Elasticity on Subduction Initiation: Insight From 2‐D Thermomechanical Models

• DOI: 10.1029/2022jb024400
• 发表时间: 2022-10
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: Xin Zhou;I. Wada