3D Characterization of the Alaska-Aleutian Subduction System with Amphibious Array Interferometry

阿拉斯加-阿留申俯冲带是北美最活跃的板块边界之一。大而多的地震、海啸和火山爆发是该地区的典型特征。这些自然灾害既有局部影响，也有深远影响。这个项目的重点是利用地震学对阿拉斯加-阿留申俯冲带的地壳和上地幔进行成像。这些数据来自阿拉斯加两栖社区地震实验，地球范围移动阵列和其他公开可用的数据。最终的阿拉斯加边缘图像将包括陆上和海上区域。这些新图像将用于提高对地震过程的了解，包括危及该州沿海人口中心的大型逆冲地震。增进对俯冲带的了解是包括地球科学家、应急管理人员和公众在内的各种利益攸关方的兴趣所在。该项目包括对两名研究生和一名本科生进行尖端地震学培训。这项工作的重点是通过将先进的地震表面波方法应用于阿拉斯加两栖社区地震实验、地球范围可移动阵列以及阿拉斯加和加拿大西北部的其他地震网络的数据，加强对阿拉斯加-阿留申俯冲系统的理解和量化。该项目的重点将是各向异性成像，以确定与俯冲系统相关的地幔流动，并量化浅层地壳物质特性，这对了解俯冲带逆冲处的同震滑动分布至关重要。各向异性成像将用于揭示俯冲驱动的地幔流动的性质，它与板块尺度流动的关系，以及它如何响应正辐合和斜辐合。地壳物理性质的变化将被记录下来，以及这些变化是否与沿着阿拉斯加-阿留申俯冲带的地震耦合变化相吻合，从而导致大逆冲地震的倾向或缺乏。将使用新的方法，包括三站直波地震干涉测量法，该方法允许在未同时部署的台站之间进行站间测量；倾斜的横向六角形各向异性，可以更完整地描述地震各向异性，而不局限于方位各向异性和表观径向各向异性；海底柔度和表面波频散的联合反演，提供了对上地壳剪切速度的约束，这是地震发生的重要因素。由此产生的模型将阐明在阿拉斯加下方逆冲的岩石圈以及上覆的地壳和地幔楔体的各向同性和各向异性特性，有助于量化俯冲带的物理特性和过程。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The Alaska-Aleutian subduction zone is one of the most active plate boundaries in North America. Large and numerous earthquakes, tsunamis, and volcanic eruptions typify the region. These natural hazards have both local and far-reaching impacts. This project focuses on using seismology to image the crust and upper mantle of the Alaska-Aleutian subduction zone. The data come from the Alaska Amphibious Community Seismic Experiment, the EarthScope Transportable Array, and other publicly available data. The resulting image of the Alaskan margin will include both onshore and offshore areas. These new images will be used to improve understanding of earthquake processes, including great megathrust earthquakes that endanger the coastal population centers of the state. Improving understanding of subduction zones is of interest to a diverse group of stakeholders including earth scientists, emergency managers, and the general public. The project includes training in cutting-edge seismology to two graduate students and one undergraduate student.The work focuses on enhanced understanding and quantification of the Alaska-Aleutian subduction system through the application of advanced seismic surface wave methods to data from the Alaska Amphibious Community Seismic Experiment, the EarthScope Transportable Array, and other seismic networks in Alaska and northwest Canada. The emphasis of the project will be on anisotropic imaging to determine mantle flow associated with the subduction system, and quantifying shallow crustal material properties essential for understanding coseismic slip distribution at subduction zone thrusts. The anisotropic imaging will be used to reveal the nature of subduction-driven mantle flow, how it relates to plate-scale flows, and how it responds to normal and oblique convergence. Variations in physical properties of the crust will be documented, and whether these coincide with variations in seismic coupling along the Alaska-Aleutian subduction zone, with resulting propensity or lack of megathrust earthquakes. Novel methodologies will be used including three-station direct wave seismic interferometry, which allows interstation measurements between stations that were not deployed at the same time; tilted transverse hexagonal anisotropy, which allows for a more complete description of seismic anisotropy not limited to azimuthal anisotropy and apparent radial anisotropy; and joint inversion of seafloor compliance and surface wave dispersion, providing shear velocity constraints on the uppermost crust which is an important contributor to seismogenesis. The resulting models will illuminate the isotropic and anisotropic properties of the lithosphere that is thrusting beneath Alaska and the overlying crust and mantle wedge, helping to quantify the physical properties and processes of 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.