Linking Surface Deformation to Slab-Mantle Flow in the Cascadia Subduction Zone through 3D Dynamic Models

在美国西北部的太平洋，太平洋下面的构造板块正沿着卡斯卡迪亚俯冲带板块边界沿着下沉到美国大陆下面。这个俯冲带被认为会产生巨大的（大于8.5级）地震和毁灭性的海啸。在过去十年中，几个项目在该地区收集了前所未有的大量数据。这些数据已经让我们深入了解俯冲几何和地幔流动。这些数据也产生了关于解释观测所需过程的问题。该项目将制作几个卡斯卡迪亚的三维高分辨率计算机模型，以探索过去一百万年来地球表面变形的历史和演变及其与地幔力的联系。这些模型的输出将与一系列观测结果进行比较，并使我们能够了解应力（地震背后的力量）是如何从下沉的板块和地幔传递到大陆的。我们还将使用这些模型来研究下沉板的结构差异如何影响应力模式。该项目支持博士后研究员。作为项目一部分开发的所有代码都将可用，对本项目使用的开放源代码所做的改进和修改将贡献回软件的主要分支。本提案旨在解决以下两个问题：1）卡斯卡迪亚板块结构与地幔流动之间的关系是什么？2）卡斯卡迪亚地幔流、上覆板块不均匀性与观测到的地壳形变之间的关系是什么？为了解决问题之一，PI将通过比较不同情况下的模型结果与地质和地球物理数据（如地震各向异性和覆盖板块中的非弧火山活动）来限制俯冲板块是否被分割成多个板块。其次，将研究Juan de Fuca板的深层结构和与表面的动态联系。第三，研究板块绝对运动对板块和上覆板块动力学的作用。为了解决第二个问题，PI将研究机械上不同的地壳岩石如何划分卡斯卡迪亚的变形。其次，将研究近期活动断层对观测变形的作用。该提案将使用卡斯卡迪亚俯冲带的最先进的高分辨率三维数值模型，以促进对应力如何在板块边界和年轻俯冲岩石圈的俯冲带中通过地幔转移的理解，以及这些应力如何导致观察到的地表变形模式并导致地震危险。该模型还将大大提高对力学异质性和观测到的变形模式之间的联系的理解覆盖plate.This奖项反映了NSF的法定使命，并已被认为是值得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的支持。

In the Pacific northwest of the U.S. the tectonic plate beneath the Pacific Ocean is sinking below the continental U.S. along the Cascadia subduction zone plate boundary. This subduction zone is known to produce giant (larger than magnitude 8.5) earthquakes and devastating tsunamis. Over the last decade several projects have collected an unprecedented amount of data in this region. These data have already given us insight into the subduction geometry and flow in Earth's mantle. The data also have generated questions about the processes needed to explain the observations. This project will make several three-dimensional, high resolution computer models of Cascadia to explore the history and evolution of deformation at the surface of the earth and its connection to forces from the mantle below over the last million years. The output of these models will be compared to a range of observations and allow us to learn how stresses (the forces behind earthquakes) are passed from the sinking plate and mantle to the continent. We will also use these models to investigate how differences in structure of the sinking plate can affect stress patterns. The project supports a postdoctoral investigator. All code developed as part of the project will be available, and improvements and modifications made to the open source code used by this project will be contributed back to the main branch of the software.This proposal aims to address the following two questions: 1) What is the relationship between slab structure and mantle flow in Cascadia? and 2) What is the relationship between mantle flow, overriding plate heterogeneity and observed crustal deformation in Cascadia? To address question one the PI will constrain whether the subducting plate is segmented into multiple slabs by comparing model results of different cases against geological and geophysical data such as seismic anisotropy and non-arc volcanism in the overriding plate. Secondly, the deep structure and dynamic link to the surface of the Juan de Fuca slab will be investigated. Thirdly, the role of absolute plate motion on the dynamics of the slab and the overriding plate will be investigated. To address the second question, the PI will look at how mechanically distinct crustal terranes partition the deformation in Cascadia. Secondly, the role of recently active faults on the observed deformation will be examined. This proposal will use state of the art high resolution 3-D numerical models of the Cascadia subduction zone to advance understanding of how stresses are transferred across the plate boundary and through the mantle in a subduction zone with young subducting lithosphere, and how these stresses lead to the observed pattern of surface deformation and contribute to seismic hazard. The models will also significantly advance understanding of the link between mechanical heterogeneity and observed deformation patterns within overriding plates.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.