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、海啸和火山喷发是该地区的典型。这些自然灾害既有局部影响，也有深远影响。该项目的重点是利用地震学成像阿拉斯加-阿留申俯冲带的地壳和上地幔。这些数据来自阿拉斯加两栖社区地震实验、地球望远镜可移动阵列和其他公开可用的数据。由此产生的阿拉斯加边缘图像将包括陆上和近海地区。这些新图像将用于提高对地震过程的理解，包括危及该州沿海人口中心的大地震。增进对俯冲带的了解对包括地球科学家、应急管理人员和普通公众在内的不同利益攸关方群体都很感兴趣。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。工作重点是通过将先进的地震面波方法应用于阿拉斯加两栖社区地震实验、EarthScope可移动阵列和阿拉斯加和加拿大西北部的其他地震台网的数据，加强对阿拉斯加-阿留申俯冲系统的了解和量化。该项目的重点将是各向异性成像，以确定与俯冲系统有关的地幔流动，并量化对于了解俯冲带逆冲带同震滑移分布至关重要的浅层地壳物质性质。各向异性成像将被用来揭示俯冲驱动的地幔流动的性质，它如何与板块尺度的流动相关，以及它如何对正常会聚和倾斜会聚做出反应。地壳物理性质的变化将被记录在案，以及这些变化是否与阿拉斯加-阿留申俯冲带地震耦合的变化相一致，从而导致大地震的倾向或缺乏。将使用新的方法，包括三站直达波地震干涉测量，使未同时部署的台站之间可以进行台间测量；倾斜的横向六角各向异性，使地震各向异性不仅限于方位各向异性和视径向各向异性；以及海底柔度和面波频散的联合反演，对作为地震成因重要因素的最上部地壳提供剪切速度限制。由此产生的模型将阐明阿拉斯加下方岩石圈和上覆地壳和地幔楔形区的各向同性和各向异性属性，帮助量化俯冲区的物理属性和过程。该奖项反映了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-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.