Collaborative Research: Fate and Consequences of Yakutat Terrane Subduction Beneath Eastern Alaska and the Wrangell Volcanic Field

兰格尔火山区是过去260万年来地球上最大的火山岩喷发区之一，但它与板块构造过程的关系仍然是个谜。阿拉斯加下面的地震位置表明，太平洋板块在俯冲过程中正在阿拉斯加下面滑动。 这些地震在兰格尔山脉以西突然停止，但不知何故，这些板块继续向东汇聚，穿过兰格尔地区，绵延数百公里。由于俯冲和造山运动之间的密切联系，南阿拉斯加地区提供了一个特殊的试验场，以测试地幔在板块结束时如何表现的理论，以及会聚如何在俯冲带发生地震。这项研究的核心是一个临时网络的37个宽带地震站部署在阿拉斯加南部，以补充地球范围移动阵列网络沿着关键断面。它提供的数据告诉是否俯冲下发生弗兰格尔，以及如何阿拉斯加-阿留申俯冲带结束。 这项研究是由一个团队进行的，该团队在通过部署地震阵列并将其结果与其他观测和模型相结合来推进我们对俯冲带的理解方面有着良好的合作记录。与岩石学家和地球动力学家的持续合作有助于将结果传播给更广泛的地球科学受众。该项目支持两名研究生的培训和专业发展，并提供了良好的实地机会，让本科生从事研究。阿拉斯加大学费尔班克斯的外展项目为该地区的学校和科学教育中心提供了结构化的联系，通过尖端的研究接触当地居民。它支持跨学科的合作，为研究人员和学生之间的持续跨学科教育提供了充足的机会。的兰格尔火山场代表了一个显着的贡献者，在北美的总喷发记录，这项研究将提供关键的框架，了解这种危害以及. Technical DescriptionThe拟议的研究是帮助显着提高我们的理解俯冲带的动力学，岩石圈俯冲的浮壳，质量守恒板扭曲，和弧火山活动的驱动程序。临时部署的37个宽带地震台站的结果侧重于确定板表面和楔形几何形状的接收器功能，除了环境噪声层析成像，速度和衰减成像，震颤和地震活动性研究，并测量剪切波分裂的各向异性。它解决了以下问题：1）阿拉斯加-阿留申板块的东端在哪里，它的结构是什么？它是以撕裂结束，还是不断地扭曲？ 2)雅库塔特地壳俯冲、张裂和兰格尔山脉的火山活动之间有什么关系？是规则的俯冲驱动了兰格尔火山活动，还是在裂缝或边缘处的流动和高温？厚的雅库塔特地壳是否连续地潜没在兰格尔山脉之下？ 3)阿留申板块末端周围的流动是什么？与较大的板块规模的流动相比，俯冲对它的驱动力有多大？研究结果被用来了解阿拉斯加下面俯冲物质的命运及其在推动火山活动和构造运动中的作用。&

Non-Technical SummaryThe Wrangell Volcanic Field is one of the largest outpourings of volcanic rocks on the planet in the past 2.6 million years, but its relationship to processes of plate tectonics remains enigmatic. Locations of earthquakes underneath Alaska indicate that the Pacific plate is sliding beneath Alaska in a process of subduction. These earthquakes stop abruptly west of the Wrangell mountains, but somehow the plates continue to converge for several hundred kilometers eastward through the Wrangell region. Because of the close connections between subduction and mountain building, the south Alaska region provides an exceptional testing ground to test theories of how the mantle behaves when slabs end, and how convergence makes earthquakes in subduction zones. The centerpiece of this study is a temporary network of 37 broadband seismic stations deployed across southern Alaska to complement the EarthScope Transportable Array network along critical transects. It is providing data to tell whether or not subduction occurs under the Wrangells, and how the Alaska-Aleutian subduction zone ends. The research is being performed by a team with a well-established collaborative track record in advancing our understanding of subduction zones by deploying seismic arrays and integrating their results with other observations and models. Ongoing collaborations with petrologists and geodynamicists are helping spread the results to a broader geoscience audience. The project supports the training and professional development of two graduate students and provides excellent field-based opportunities to engage undergraduates in research. Outreach programs at the University of Alaska Fairbanks provide structured links to schools and science education centers in the region, reaching native populations with cutting-edge research. It supports an interdisciplinary collaboration with ample opportunity for the continued cross-disciplinary education among researchers and students. The Wrangell Volcanic Field represents a significant contributor to the total eruptive record in North America, and this study will provide critical framework for understanding this hazard as well.Technical DescriptionThe proposed research is aiding significantly in improving our understanding of the dynamics of subduction zones, the response of lithosphere to subduction of buoyant crust, mass conservation in slab contortions, and the drivers of arc volcanism. Results from the temporary deployment of 37 broadband seismic stations focus on determining slab surface and wedge geometry from receiver functions in addition to ambient noise tomography, velocity and attenuation imaging, tremor and seismicity studies, and measuring anisotropy from shear wave splitting. It addresses the following questions: 1) Where is the eastern end of the Alaska-Aleutian slab, and what is its configuration? Does it end as a tear, or is it continuously warped? 2) What is the relationship between Yakutat crust subduction, transtension, and volcanism in the Wrangell mountains? Does regular subduction drive Wrangell volcanism, or flow and high temperatures at a tear or edge? Does thick Yakutat terrane crust subduct continuously beneath the Wrangell mountains? 3) What is the flow around the end of the Aleutian slab and how much is it driven by subduction versus larger plate-scale flow? Results are being used to understand the fate of subducted material beneath Alaska and its role in driving volcanism
 and tectonics.