Collaborative Proposal: Understanding Subduction Systems by Linking Anisotropic Seismic Imaging and Geodynamic Modeling

合作提案：通过连接各向异性地震成像和地球动力学建模来了解俯冲系统

• 批准号: 1520694
• 负责人: Douglas Toomey
• 金额: $ 16.8万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1520694&HistoricalAwards=false
• 关键词: Collaborative; Proposal; Understanding; Subduction; Systems

Recordings of distant earthquakes will be used in this project to infer the velocity at which the waves traveled beneath the Earth's surface. In turn, we use this information to understand the Earth's structure and, in particular, how subduction (the descent of an old tectonic plate into the Earth's mantle) produces volcanism and affects surface topography. When conducting this type of study, it is currently common to assume that the speed at which the waves travel is independent of their direction. In reality, seismic waves travel at different speeds depending on what their direction is relative to the orientation of minerals in the mantle. This phenomenon is known as anisotropy, and when not taken into account, it can bias the image of the subsurface in ways that can compromise the understanding of the subduction processes. In this project, seismologists will investigate ways to reduce this problem by incorporating physically-based estimates of the distribution of anisotropy into the imaging procedures. In this way, more accurate images of the subsurface will be determined advancing the understanding of how subduction affects the surface, including the distribution of volcanism.The project will combine travel-time tomography, SKS splitting observations and geodynamic flow modeling to produce self-consistent models of mantle structure (isotropic and anisotropic) in the vicinity of two subduction zones. The new approach will allow us to fully integrate mantle anisotropy into teleseismic tomography of subduction zones. By incorporating estimates of the anisotropy field into travel-time tomography the scientitists will significantly reduce major artifacts stemming from the isotropic assumption and obtain a physically-based model for the strain in the mantle wedge and beneath the subducting plate. The improved imaging will allow to better recover the mantle physical state (temperature, composition and melt fraction). This methodology will be applied to existing data from the western Mediterranean and Cascadia subduction zones.

在这个项目中，远距离地震的记录将被用来推断波在地球表面下传播的速度。反过来，我们利用这些信息来了解地球的结构，特别是俯冲(旧构造板块下降到地幔中)如何产生火山作用并影响地表地形。在进行这种类型的研究时，目前普遍认为波的传播速度与其方向无关。在现实中，地震波以不同的速度传播，这取决于它们的方向相对于地幔中矿物的方向。这种现象被称为各向异性，如果不考虑这种现象，它可能会对地下表面的图像产生偏差，从而影响对俯冲过程的理解。在这个项目中，地震学家将研究通过将基于物理的各向异性分布估计纳入成像程序来减少这一问题的方法。通过这种方式，将确定更准确的地下图像，以促进对俯冲如何影响地表的理解，包括火山的分布。该项目将结合旅行时间层析成像、SKS分裂观测和地球动力学流动模拟，产生两个俯冲带附近的地幔结构(各向同性和各向异性)的自洽模型。这种新方法将使我们能够将地幔各向异性完全整合到俯冲带的远震层析成像中。通过将各向异性场的估计合并到旅行时层析成像中，科学家们将显着减少各向同性假设产生的主要伪影，并获得地幔楔形和俯冲板块下方的应变的物理模型。改进的成像将允许更好地恢复地幔的物理状态(温度、成分和熔体分数)。这一方法将适用于地中海西部和卡斯卡迪亚俯冲带的现有数据。