Integrating Marine Seismic and Ocean Drilling Results with three-dimensional dynamic models of Subduction Initiation

将海洋地震和海洋钻探结果与俯冲起始的三维动态模型相结合

• 批准号: 2049086
• 负责人: Michael Gurnis
• 金额: $ 35.16万
• 依托单位: California Institute of Technology
• 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: 2021-01-01 至 2024-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2049086&HistoricalAwards=false
• 关键词: Integrating; Marine; Seismic; Ocean; Drilling

This project seeks to better understand a process called subduction. Subduction is where cold oceanic plates return to Earth’s interior. Plate subduction is a key geological process responsible for the largest forces on tectonic plates, the site of the most destructive earthquakes on the planet and leads to much of the volcanism on Earth’s surface. The project will look at the process of forming a new subduction zone, which is called subduction initiation. Subduction initiation is poorly understood but is associated with the largest changes in the forces which both drive and resist plate tectonic motions. Although many aspects of plate tectonics are understood, subduction initiation remains a key unknown and there has been a concerted effort in the last few years to understand this process through marine geological and geophysical research. This project will synthesize the recent marine research with what are called plate tectonic reconstructions and incorporate that information into computational models. Some of the key evidence that constrains the process has come from deep sea drilling and through marine seismic surveys. These data constrain the details of the geological evolution and present-day structure of the sites of subduction initiation, respectively. The project will focus on four sites of recent or on-going subduction initiation: Izu-Bonin Mariana south of Japan, Tonga Kermadec in the southwest Pacific, Puysegur south of New Zealand and Matthews-Hunter near Fiji also in the southwest Pacific. It has recently been discovered through ocean drilling that the Izu-Bonin-Mariana and the Tonga-Kermadec subduction zones may have initiated at the same time despite being separated by several thousand miles and were associated with a major change in the motion of the Pacific Plate. This project will look at the details of how these subduction zones formed in terms of the basic physics of solid and fluid mechanics. During subduction initiation, the so-called mega thrust fault, the site of destructive great earthquakes, forms. It is thought that such a new megathrust is in the process of forming south of New Zealand. In this project sophisticated computational methods, call finite elements, will be used and will use the largest supercomputers supported by the National Science Foundation. During the project, a graduate student will be trained in computational methods, which are widely applicable to many areas of science and engineering. The investigator will work with the Caltech Seismo Lab Outreach and Social Media office to communicate science to the broad, diverse community of the Los Angeles community, including through visits to local public schools. The initiation of new subduction zones is a key component of plate tectonics but remains an unsolved problem. With subducted slabs being the primary force driving plate motions, formation of new subduction zones and demise of existing ones are associated with the largest changes in the forces on tectonic plates. There was an ocean basin-wide tectonic change in the Pacific at about 50 Ma with initiation of IBM and Tonga-Kermadec synchronous with a change in plate motions. This project will squarely address these fundamental problems by exploiting the recently expanded observational record from deep sea drilling and marine seismic surveys. The team of geoscientists will test concepts for the initiation of subduction by comparing observations against a new generation of 3D, time-dependent geodynamic models. With the observational constraints on subduction initiation through ocean drilling and marine seismic surveys jumping forward over the last six years simultaneous with a commensurate maturing of software and computational hardware, the time is ideal to readdress the mechanics of subduction initiation. The investigators will build detailed regional plate tectonic reconstructions (data models) for four western Pacific subduction initiation events: Izu-Bonin Mariana (IBM), Tonga Kermadec, Puysegur and Matthews-Hunter. The Puysegur subduction zone (offshore New Zealand) is an ideal natural laboratory for testing the mechanics of subduction initiation with its well-constrained plate kinematics, structural controls, stress evolution, vertical motions, and distribution of faults. These reconstructions provide essential initial and boundary conditions and allow for rigorous comparisons between geodynamic models and geological and geophysical observations. The finite element method will be used for the solution of these inherently time-dependent, multi-scale problems and achieve the resolutions required to track the localization of deformation key for systems with plastic failure. The visco-elastoplastic models will have thermal and compositional buoyancy and explicit sub-scale models of weakening, dislocation creep, and partial melting. The team will constrain, slab strength, stress propagation, plastic failure and fault zone nucleation (weakening mechanisms associated with grain evolution and sperpentinization) from time-dependent models with plate motions for Puysegur since 15 Ma and Matthews-Hunter since 2 Ma. The team will determine the conditions needed to initiate the IBM arc at 52 Ma over 100-1,000 km of strike such that the initial magmatic signal is synchronous within a few Myrs. For IBM, the rate at which driving forces grow and are transmitted to the Pacific plate will be addressed. The project will reach a new level of integration between dynamic flow models, plate kinematics and MG&G data that could have broad application. The work could impact several large programs. The geodynamic hypotheses could result in predictions that could be tested with deep sea drilling under the auspices of IODP.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.

该项目旨在更好地理解俯冲过程。俯冲是寒冷的海洋板块返回地球内部的地方。板块俯冲是一个关键的地质过程，它对构造板块产生最大的作用力，而构造板块是地球上最具破坏性的地震发生地，并导致地球表面的大部分火山活动。该项目将研究形成新俯冲带的过程，称为俯冲起始。人们对俯冲起始知之甚少，但它与驱动和抵抗板块构造运动的力的最大变化有关。尽管板块构造的许多方面已被了解，但俯冲起始仍然是一个关键的未知数，并且在过去几年中，人们一致努力通过海洋地质和地球物理研究来了解这一过程。该项目将综合最近的海洋研究与所谓的板块构造重建，并将这些信息纳入计算模型中。限制这一过程的一些关键证据来自深海钻探和海洋地震调查。这些数据分别限制了俯冲起始地点的地质演化和现今结构的细节。该项目将重点关注最近或正在进行的俯冲启动的四个地点：日本南部的伊豆-博宁马里亚纳、西南太平洋的汤加克马德克、新西兰南部的皮塞古尔和西南太平洋斐济附近的马修斯-亨特。最近通过大洋钻探发现，伊豆-小博宁-马里亚纳和汤加-克马德克俯冲带可能是同时开始的，尽管相距数千英里，并且与太平洋板块运动的重大变化有关。该项目将根据固体和流体力学的基本物理学来研究这些俯冲带如何形成的细节。在俯冲起始过程中，形成了所谓的巨型逆冲断层，即破坏性大地震的发生地。据认为，这样一个新的巨型逆冲断层正在新西兰南部形成。在该项目中，将使用称为有限元的复杂计算方法，并将使用美国国家科学基金会支持的最大超级计算机。在该项目期间，研究生将接受计算方法的培训，这些方法广泛适用于科学和工程的许多领域。调查员将与加州理工学院地震实验室外展和社交媒体办公室合作，向洛杉矶社区广泛、多元化的社区传播科学知识，包括访问当地公立学校。新俯冲带的形成是板块构造的一个关键组成部分，但仍然是一个未解决的问题。由于俯冲板片是驱动板块运动的主要力，新俯冲带的形成和现有俯冲带的消亡与构造板块上的力的最大变化有关。大约 50 Ma 时，太平洋发生了一次洋盆范围的构造变化，IBM 和汤加-克马德克的启动与板块运动的变化同步。该项目将通过利用最近扩大的深海钻探和海洋地震勘测观测记录来解决这些基本问题。地球科学家团队将通过将观测结果与新一代 3D 随时间变化的地球动力学模型进行比较，来测试俯冲启动的概念。随着过去六年中通过海洋钻探和海洋地震勘测对俯冲引发的观测限制不断向前发展，同时软件和计算硬件也相应成熟，现在是重新解决俯冲引发机制的理想时机。研究人员将为四个西太平洋俯冲起始事件建立详细的区域板块构造重建（数据模型）：伊豆-博南马里亚纳（IBM）、汤加克马德克、皮塞古尔和马修斯-亨特。皮塞古尔俯冲带（新西兰近海）是测试俯冲起始机制及其良好约束的板块运动学、结构控制、应力演化、垂直运动和断层分布的理想天然实验室。这些重建提供了必要的初始条件和边界条件，并允许在地球动力学模型与地质和地球物理观测之间进行严格比较。有限元方法将用于解决这些本质上与时间相关的多尺度问题，并实现跟踪塑性失效系统变形关键定位所需的分辨率。粘弹塑性模型将具有热浮力和成分浮力以及弱化、位错蠕变和部分熔化的显式子尺度模型。该团队将根据 Puysegur 自 15 Ma 以来的板块运动和 Matthews-Hunter 自 2 Ma 以来的板块运动的时间相关模型来约束板坯强度、应力传播、塑性破坏和断层带成核（与晶粒演化和云纹石化相关的弱化机制）。该团队将确定在 100-1,000 公里的冲击范围内以 52 Ma 启动 IBM 弧所需的条件，以便初始岩浆信号在几 Myrs 内同步。对于 IBM 来说，驱动力增长并传递到太平洋板块的速度将得到解决。 该项目将在动态流动模型、板运动学和 MG&G 数据之间达到新的集成水平，从而具有广泛的应用。 这项工作可能会影响几个大型项目。地球动力学假设可以得出可以在 IODP 的支持下通过深海钻探进行测试的预测。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Strike slip motion and the triggering of subduction initiation

• DOI: 10.3389/feart.2023.1156034
• 发表时间: 2023-04
• 作者: Yida Li;M. Gurnis

A simple force balance model of subduction initiation

俯冲起始的简单力平衡模型

• DOI: 10.1093/gji/ggac332
• 发表时间: 2022
• 期刊: Geophysical Journal International
• 影响因子: 2.8
• 作者: Li, Yida;Gurnis, Michael
• 通讯作者: Gurnis, Michael