RUI: Lithospheric Velocity Structure and Anisotropy of the Alaskan Subduction Margin

RUI：阿拉斯加俯冲边缘的岩石圈速度结构和各向异性

• 批准号: 1955558
• 负责人: Aubreya Adams
• 金额: $ 24.58万
• 依托单位: Colgate University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-06-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1955558&HistoricalAwards=false
• 关键词: RUI; Lithospheric; Velocity; Structure; Anisotropy

The southern coast of Alaska is the most seismically and volcanically active portion of the United States, and was home to the second largest earthquake recorded anywhere on Earth. The behavior of earthquakes and volcanos, however, changes dramatically between regions along the coast. Some areas produce extremely large earthquakes, while other regions have only small to moderate-sized earthquakes. Similarly, the chemistry and eruption styles of volcanos change along the coast. Understanding the origins of these differences could lead to important insights into global earthquake and volcano hazards. Scientists believe that the key to understanding this system may lie in the structure and fluid-content of rocks 100-200 km beneath the surface, where the Pacific tectonic plate dives beneath the North America tectonic plate. This study will use earthquake waves to image these rocks buried under Alaska’s coast. These waves, called surface waves, travel across the earth near the surface and change speeds based on the characteristics of the rocks that they travel through. By measuring differences in wave speed based on location and the direction the waves travel, we will examine whether differences in earthquake and volcano behavior are connected to (a) changes in magma-production regions, (b) changes in the fluid content of rocks, or (c) changes in the direction that rocks slowly flow deep beneath the surface. The work will be completed at a Primarily Undergaduate Institution and provides research experience for undergraduate students. The project also supports the training of an early career Postdoctoral Investigator.The subduction zone along the southern margin of Alaska is home to numerous active volcanos, and is the most seismically active portion of the United States. It has hosted several megathrust earthquakes, including the 1964 Great Alaskan Earthquake, the second largest earthquake in recorded history. The seismic and volcanic behavior of the subduction zone, however, undergoes dramatic changes along strike, with some areas slipping in great (M8) events while other regions deform primarily through creep. Understanding the origins of this variability could lead to important insights into subduction zone processes and global geophysical hazards. Recent studies have highlighted the role that hydration of the subducting slab and the mantle wedge may play in governing these behaviors. In this study, recently collected data from the Alaska Amphibious Community Seismic Experiment and the Alaska Transportable Array will be leveraged to build Rayleigh and Love wave velocity models and to solve for radial and azimuthal anisotropy of shear waves in the upper mantle beneath the Alaskan subduction zone. These velocity models will be used to determine how forearc mantle structure, hydration of the incoming plate and the mantle wedge, and mantle flow combine to influence volcanic and seismic behavior along the subduction zone.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.

阿拉斯加南部海岸是美国地震和火山活动最活跃的地区，也是地球上有记录以来第二大地震的发生地，但沿海地区之间的地震和火山活动却发生了巨大变化。一些地区会发生特大地震，而另一些地区只会发生小到中型地震。同样，了解这些差异的根源可以让科学家们对全球地震和火山灾害产生重要的认识。相信理解这一系统的关键可能在于地表以下 100-200 公里处岩石的结构和流体含量，太平洋构造板块潜入北美构造板块下方。这项研究将利用地震波对埋在地下的这些岩石进行成像。阿拉斯加的海岸，这些波被称为表面波，在地球表面附近传播，并根据其传播的岩石的特性改变速度。通过测量波速的差异，我们将根据波传播的位置和方向来计算。检查是否存在差异地震和火山行为的变化与（a）岩浆产生区域的变化，（b）岩石流体含量的变化，或（c）岩石在地表深处缓慢流动的方向的变化有关。主要在本科院校完成，为本科生部分提供研究经验。该项目还支持早期职业博士后研究员的培训。阿拉斯加南缘的俯冲带是众多活火山的所在地，也是地震最活跃的地区。美国的。几次大逆冲地震，包括 1964 年阿拉斯加大地震，这是有记录以来的第二大地震，然而，俯冲带的地震和火山行为在走向过程中经历了巨大的变化，一些地区在大（M8）事件中发生滑落，而其他地区则发生了滑落。了解这种变化的起源可能有助于深入了解俯冲带过程和全球地球物理危害。最近的研究强调了俯冲板片和地幔水合作用的作用。在这项研究中，最近从阿拉斯加两栖社区地震实验和阿拉斯加可运输阵列收集的数据将被用来建立瑞利和洛夫波速度模型，并解决剪切波的径向和方位各向异性。这些速度模型将用于确定弧前地幔结构、传入板块和地幔楔的水合作用以及地幔流如何综合影响。该奖项反映了 NSF 的法定使命，并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，被认为值得支持。