Collaborative Research: Investigating formation of stagnant slabs and implications for subduction dynamics

合作研究：调查静止板片的形成及其对俯冲动力学的影响

• 批准号: 2244661
• 负责人: Jeroen Tromp
• 金额: $ 43.25万
• 依托单位: Princeton University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-02-01 至 2026-01-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2244661&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; formation; stagnant

Many decades have passed since the establishment of the theory of plate tectonics. Scientists still debate how tectonic plates recycling into Earth’s interior evolve over time as they descend. Advances in generating 'seismic tomographic images' of the Earth (analogous to medical CT scans) provide increasingly detailed images of these foundered plates (or 'slabs'), many of which are trapped about 300 to 600 miles below the Earth's surface. These images represent a present-day snapshot of the convecting mantle, and its evolution over time may be investigated through numerical modeling of the subduction process. This collaborative proposal combines recent developments in data-driven modeling and seismic tomography. Liu, Tromp, and their graduate students will explore different ways that subducted slabs get trapped in the mid mantle, with a focus on two competing hypotheses: that the slab is being pulled by one end which is stuck to a plate at the surface, or (2) that it is dragged along with horizontal flow of the surrounding mantle. This research will improve our understanding of how the Earth's mantle flows, and how it has flowed (and how the Earth's plates have moved) over tens of millions of years. Sophisticated software for modeling the slabs and imaging the mantle will be significantly improved and freely shared with other scientists via public websites.Extensive fast seismic anomalies within the 500-1000 km mantle depth range are called stagnant slabs, and their origin has implications for continental tectonics and mantle dynamics. A commonly invoked mechanism is trench retreat, but the observed amount of retreat does not always match simulations. Another frequently made assumption is that slabs sink vertically, even though this can violate geological observations. A potential solution to these problems is to consider lateral mantle flow at mid-mantle depths, whose effect on slab stagnation remains poorly explored. Another complication is the inconsistency of tomographic images of the present-day configuration of stagnant slabs. The PI teams will collaboratively evaluate dynamic effects of trench retreat and lateral mantle flow on slab stagnation by designing 3D spherical Earth models through sequential data assimilation (SDA) and comparing the results with improved tomographic images using full-waveform inversion (FWI) with source encoding. The SDA modeling approach is appropriate for testing key controlling parameters for slab stagnation while simultaneously considering many other natural complexities. The improved FWI method increases seismic resolution significantly at upper-to-mid mantle depths, where stagnant slabs reside. Through a set of SDA models that test the available range of trench motion histories at different geographic locations implemented in both regional- and global-scale simulations, the teams will quantify the respective contributions of trench retreat and lateral mantle flow on the formation of observed stagnant slabs. Ultimately, this exercise will generate new insight into subduction dynamics and the associated tectonic records.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.

自建立板块构造理论以来，已经过去了数十年。科学家们仍在辩论如何随着时间的流逝，如何回收到地球内部进化。生成地球的“地震层析成像图像”（类似于医学CT扫描）的进步提供了这些基础板（或“平板”）的越来越详细的图像，其中许多被困在地球表面以下约300至600英里处。这些图像代表了对流地幔的当前快照，并且可以通过俯冲过程的数值建模来研究其随时间的演变。该协作提案结合了数据驱动建模和地震层析成像的最新发展。刘，特罗姆和他们的研究生将探索俯冲板被困在中壁架中的不同方式，重点是两个相互竞争的假设：将板拉动的一端被粘在表面上的盘子上，或（2）与周围周围地幔的水平流动在一起。这项研究将提高我们对地球地幔如何流动的理解，以及它如何流动（以及地球板的移动方式）在数百万年内。用于建模板和成像地幔的复杂软件将通过公共网站显着改善并自由地与其他科学家共享。扩展的快速地震异常在500-1000公里的地幔深度范围内称为停滞板，其起源对持续的构造和壁炉动力学有影响。通常调用的机制是沟渠撤退，但是观察到的撤退量并不总是与模拟相匹配。另一个经常做出的假设是，即使这可能违反地质观察，平板也垂直下沉。解决这些问题的一种潜在解决方案是考虑在中间深度处的侧面地幔流，其对平板停滞的影响仍然很差。另一个并发症是停滞板的当今配置的层析成像图像的不一致。 PI团队将通过连续数据同化（SDA）设计3D球形地球模型（SDA），通过设计3D球形地球模型（SDA）协作评估沟槽撤退和侧壁流对平板停滞的动态效应，并使用全波形倒置（FWI）将结果与改进的层析成像图像与源编码进行比较。 SDA建模方法适用于测试密钥控制参数以进行平板停滞，同时考虑许多其他自然复杂性。改进的FWI方法可在上层地幔深处显着提高地震分辨率，其中停滞的平板驻留。通过一组SDA模型，这些模型在区域和全球尺度模拟中实现的不同地理位置上可用的沟槽运动历史范围，这些团队将量化沟槽撤退和侧壁流的各自的贡献，并在观察到的Stagnant板块的形成中量化。最终，该练习将对俯冲动态和相关的构造记录产生新的见解。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响审查标准，认为通过评估被认为是宝贵的支持。