Anisotropic imaging of the Alaska-Aleutian subduction zone from shear wave splitting analyses

阿拉斯加-阿留申俯冲带是北美构造最活跃的会聚边缘，代表着一个具有科学意义和社会意义的地区。该地区曾发生过几次巨大的逆冲地震，火山活动频繁，并有可能引发海啸。该地区也是研究俯冲系统的理想天然实验室，因为太平洋板块长期俯冲，与形成阿留申群岛的俯冲相关的火山作用，以及强烈的地震活动。该项目将利用陆上和近海地震数据研究驱动俯冲的地幔过程。将在俯冲系统的不同部分内检查地幔变形。将要使用的技术是相辅相成的，当它们结合在一起时，将提供俯冲带地区的全貌。这一综合观点将允许对不同俯冲区的运作和相互作用进行调查，以创建今天所看到的阿拉斯加-阿留申俯冲带。该项目将把一名本科生带到特拉华大学进行暑期研究实习，并为博士生提供培训。该项目还将包括与特拉华大学灾害研究中心的协作外联活动。该项目是对整个阿拉斯加-阿留申俯冲带(AASZ)的地震各向异性的多方面研究。将按顺序使用多个数据集和技术，以深入了解俯冲系统不同部分的相互作用。将对各种地震阶段进行横波分裂分析，每个阶段都是为最好地评估亚洲自贸区的一部分而量身定做的：1)以地幔楔体为目标的岛弧站的局部S分裂，2)隔离下行板块内变形的几何形状的震源一侧分裂，3)以次板块地幔动力学为目标的震源一侧分裂，以及4)海底和陆地站的传统分裂。每组分裂观测以特定的俯冲带区域为目标，并带有相关的针对性问题，以便于整合在一起的方式。将这套互补技术结合在一起，将创建导致现代AASZ的变形和活动动力学的完整视图。这些结果将加深对地幔中的板块变形、地幔楔形动力学和弧岩浆活动中沿走向变化的联系的理解，以及太平洋下地幔流动从表层板块转变为俯冲板块的整体演化。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The Alaska-Aleutians subduction zone is the most tectonically active convergent margin in North America and represents an area of both scientific and societal relevance. The region has hosted several large mega-thrust earthquakes, has a lot of volcanic activity, and has the potential of generating a tsunami. The region is also an ideal natural laboratory to study subduction systems due to the long-term subduction of the Pacific Plate, volcanism associated with subduction that builds the Aleutian Islands, and high earthquake activity. This project will examine the mantle processes that drive subduction using both onshore and offshore earthquake data. Mantle deformation will be examined within the different portions of the subduction system. The techniques to be used are complementary and when combined will provide a full picture of the subduction zone region. This integrated view will allow an investigation of the operation and interactions of the different subduction regions to create the Alaska-Aleutians subduction zone that is seen today. This project will bring an undergraduate student to the University of Delaware for a summer research experience internship and will provide training for a doctoral student. This project also will include collaborative outreach activities with the University of Delaware Disaster Research Center. This project is a multi-faceted examination of seismic anisotropy throughout the Alaska-Aleutians subduction zone (AASZ). Multiple datasets and techniques will be used in sequence to gain insights into the interactions of the different parts of the subduction system. Shear wave splitting analyses will be performed on a variety of seismic phases that are each tailored to best assess a portion of the AASZ: 1) local-S splitting at island arc stations that target the mantle wedge, 2) source-side splitting in geometries that isolate deformation within the downgoing slab, 3) source-side splitting that targets dynamics in the sub-slab mantle, and 4) traditional splitting at the ocean-bottom and onland stations. Each set of splitting observations targets a specific subduction zone region, with associated targeted questions, in such a way as to be easily integrated together. Combining the suite of complementary techniques will create a complete view of the deformation and active dynamics leading to the modern day AASZ. These results will refine the understanding of slab deformation in the mantle, the association of mantle wedge dynamics and along strike variations in arc magmatism, and the overall evolution of mantle flow beneath the Pacific as it morphs from a surface plate into a subducting slab.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.