Origin of seismic heterogeneity and attenuation in the Earth's upper mantle and transition zone

地球上地幔和过渡带地震非均质性和衰减的成因

• 批准号: NE/K005669/1
• 负责人: Ana Ferreira
• 金额: $ 37.67万
• 依托单位: University College London
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2014
• 资助国家: 英国
• 起止时间: 2014 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FK005669%2F1
• 关键词: Origin; seismic; heterogeneity; attenuation; Earth

The Earth is a dynamic planet with a changing surface partly shaped by processes in its deep interior, which control earthquakes, volcanoes and the formation of mountain ranges. Flow in the Earth's uppermost mantle and transition zone (at depths of ~50-660 km beneath the surface) drives plate tectonics, one of the features distinguishing our planet from others. However, there is much that we do not know about the Earth's mantle: What are the scales of variation in the properties of the Earth? Is variation in the structure of the mantle due to temperature and/or chemical composition? In what directions does mantle flow? Recent developments in seismology, thermodynamic modelling and rock physics have the potential to help solve these questions. Modern high performance computing is enabling the efficient analysis and modelling of freely-available large-scale sets of seismic data from around the world allowing us to generate increasingly detailed images of the Earth's interior. Progress in rock and mineral physics laboratory experiments, along with new developments in thermodynamic theory, now allow the construction of realistic models of planetary interiors that are thermodynamically self-consistent. As a result of the joint use of these different techniques, properties of the Earth that were very difficult to estimate in the past are within reach today. Intrinsic seismic attenuation (the amplitude loss of propagating seismic waves due to internal friction or anelastic processes) is particularly interesting, giving unique insight about temperature, chemical composition and the presence of fluids in the Earth's mantle when jointly interpreted using seismology, mineral/rock physics and geodynamics. However, up to now, seismic attenuation has received relatively little attention, and efforts for such integrated studies of the Earth's interior have been rare and limited. This project addresses these issues, with the aim of substantially advancing our fundamental understanding of the physical and chemical processes occurring in the Earth's interior, notably in the uppermost mantle and transition zone. We will achieve this by assembling a new massive seismic dataset, which will be modelled and used for the first time along with novel thermodynamical and rock physics information in a fully consistent way, to build new global 3-D images of attenuation and seismic speed in the Earth's mantle, and infer mantle's temperature, chemical composition and flow. This will help us deduce the scale, distribution and mechanisms responsible for variations in Earth's properties and attenuation in the upper mantle and transition zone, leading to an improved understanding of the dynamics of this key component of the deep Earth. We have gathered a team of three UK scientists with complementary expertise in seismology, geodynamics and mineral physics, supported by international multidisciplinary partners, with the skills and knowledge to build a new framework for the 3-D seismo-thermodynamic characterization of the Earth's interior. We will build on our recent work in novel seismic data analysis and imaging strategies, and on mineralogical and dynamical mantle modelling. By the end of this 3-year research project, with help from two postdoctoral assistants, we will have new knowledge about the dynamic processes in the Earth's mantle, and new tools and frameworks for integrated deep Earth research, which will be widely disseminated beyond the project's duration. So far no studies of 3-D attenuation, seismic speed, temperature, chemical composition and flow in the Earth's upper mantle and transition zone have used such a comprehensive, interdisciplinary approach.

地球是一颗动态的行星，其表面不断变化，部分是由其内部深处的过程所塑造的，这些过程控制着地震、火山和山脉的形成。地球最上层地幔和过渡带（地表以下约 50-660 公里的深度）的流动驱动着板块构造，这是我们星球区别于其他星球的特征之一。然而，关于地幔，我们还有很多不了解的地方：地球特性的变化范围有多大？地幔结构的变化是由于温度和/或化学成分造成的吗？地幔向哪些方向流动？地震学、热力学建模和岩石物理学的最新发展有可能帮助解决这些问题。现代高性能计算能够对世界各地免费提供的大规模地震数据集进行有效分析和建模，使我们能够生成越来越详细的地球内部图像。岩石和矿物物理实验室实验的进展以及热力学理论的新发展，现在允许构建热力学自洽的行星内部的真实模型。由于这些不同技术的联合使用，过去很难估计的地球特性现在已经可以实现。固有地震衰减（由于内摩擦或滞弹性过程而导致传播地震波的振幅损失）特别有趣，当使用地震学、矿物/岩石物理学共同解释时，它可以提供关于地幔中温度、化学成分和流体存在的独特见解和地球动力学。然而，到目前为止，地震衰减受到的关注相对较少，对地球内部进行此类综合研究的努力也很少且有限。该项目致力于解决这些问题，旨在大幅推进我们对地球内部（特别是最上地幔和过渡带）发生的物理和化学过程的基本理解。我们将通过组装一个新的大规模地震数据集来实现这一目标，该数据集将首次以完全一致的方式与新的热力学和岩石物理信息一起进行建模和使用，以构建新的衰减和地震速度的全球 3D 图像。地球的地幔，并推断地幔的温度、化学成分和流动。这将帮助我们推断造成地球性质变化以及上地幔和过渡带衰减的规模、分布和机制，从而更好地了解地球深处这一关键组成部分的动力学。我们聚集了一支由三名英国科学家组成的团队，他们在地震学、地球动力学和矿物物理学方面具有互补的专业知识，并得到国际多学科合作伙伴的支持，拥有为地球内部 3D 地震热力学表征建立新框架的技能和知识。我们将基于我们最近在新颖的地震数据分析和成像策略以及矿物学和动态地幔建模方面的工作。到这个为期3年的研究项目结束时，在两名博士后助理的帮助下，我们将获得有关地幔动态过程的新知识，以及用于综合地球深部研究的新工具和框架，这些知识将在地球以外广泛传播。项目的持续时间。迄今为止，还没有对地球上地幔和过渡带的三维衰减、地震速度、温度、化学成分和流动的研究使用过如此全面的跨学科方法。

项目成果

Ubiquitous lower-mantle anisotropy beneath subduction zones

俯冲带下普遍存在的下地幔各向异性

• DOI: 10.1038/s41561-019-0325-7
• 发表时间: 2019-03-25
• 期刊: Nature Geoscience
• 影响因子: 18.3
• 作者: A. Ferreira;M. Faccenda;W. Sturgeon;Sung‐Joon Chang;L. Schardong
• 通讯作者: L. Schardong

Extrinsic Elastic Anisotropy in a Compositionally Heterogeneous Earth's Mantle.

成分异质的地幔中的外在弹性各向异性。

• DOI: http://dx.10.1029/2018jb016482
• 发表时间: 2019
• 期刊: Journal of geophysical research. Solid earth
• 作者: Faccenda M

Joint inversion for global isotropic and radially anisotropic mantle structure including crustal thickness perturbations

全球各向同性和径向各向异性地幔结构的联合反演，包括地壳厚度扰动

• DOI: 10.1002/2014jb011824
• 发表时间: 2015-06-01
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: Sung‐Joon Chang;A. Ferreira;J. Ritsema;H. J. Heijst;J. Woodhouse
• 通讯作者: J. Woodhouse

The Evolution of Mantle Plumes in East Africa

东非地幔柱的演化

• DOI: 10.1029/2020jb019929
• 发表时间: 2020-11-04
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: Sung‐Joon Chang;E. Kendall;A. Davaille;A. Ferreira
• 通讯作者: A. Ferreira

Crustal structure beneath Portugal from teleseismic Rayleigh Wave Ellipticity

远震瑞利波椭圆度显示葡萄牙下方的地壳结构

• DOI: http://dx.10.1016/j.tecto.2017.06.001
• 发表时间: 2017
• 期刊: Tectonophysics
• 影响因子: 2.9
• 作者: Attanayake J