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/K006061/1
• 负责人: Carolina Lithgow-Bertelloni
• 金额: $ 27.44万
• 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: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FK006061%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.

地球是一个充满活力的星球，其表面不断变化，部分原因是其内部深处的过程，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公里深处）的流动驱动着板块构造，这是我们的星球区别于其他星球的特征之一。然而，我们对地球的地幔还有很多不了解：地球性质的变化尺度是什么？地幔结构的变化是由温度和/或化学成分引起的吗？地幔是朝什么方向流动的？地震学、热力学模型和岩石物理学的最新发展有可能帮助解决这些问题。现代高性能计算使来自世界各地的免费大规模地震数据集的有效分析和建模成为可能，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，沿着热力学理论的新发展，现在允许构建行星内部的物理自洽的现实模型。由于联合使用了这些不同的技术，过去很难估计的地球性质今天已经可以得到。内在地震衰减（由于内部摩擦或滞弹性过程导致的传播地震波的振幅损失）特别有趣，当使用地震学，矿物/岩石物理学和地球动力学联合解释时，对温度，化学成分和地幔中流体的存在提供了独特的见解。然而，到目前为止，地震衰减受到的关注相对较少，对地球内部的这种综合研究的努力很少和有限。该项目解决这些问题，目的是大大提高我们对地球内部，特别是最上层地幔和过渡带发生的物理和化学过程的基本认识。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，该数据集将以完全一致的方式与新的岩石和岩石物理信息一起进行建模和沿着使用，以建立新的全球地幔衰减和地震速度的3D图像，并推断地幔的温度，化学成分和流动。这将有助于我们推断出造成地球性质变化和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部这一关键组成部分的动态。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，并得到了国际多学科合作伙伴的支持，拥有为地球内部的三维地震热力学特征建立新框架的技能和知识。我们将建立在我们最近的工作在新的地震数据分析和成像策略，并在矿物学和动力学地幔建模。在这个为期3年的研究项目结束时，在两名博士后助理的帮助下，我们将获得有关地球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，这些工具和框架将在项目结束后广泛传播。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、化学成分和流动进行过这样全面的跨学科研究。