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。大规模的地震、海啸和火山爆发是该地区的典型特征。这些自然灾害既有地方性的影响，也有深远的影响。该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，EarthScope便携式阵列和其他公开数据。由此产生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理解，包括危及该州沿海人口中心的大型逆冲断层地震。提高对俯冲带的认识是包括地球科学家、应急管理人员和公众在内的各种利益相关者的兴趣所在。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，工作重点是通过对阿拉斯加两栖社区地震实验、EarthScope移动式阵列以及阿拉斯加和加拿大西北部其他地震网络的数据应用先进的地震表面波方法，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，以确定与俯冲系统相关的地幔流，并量化浅地壳材料特性，这对于了解俯冲带逆冲断层的同震滑动分布至关重要。各向异性成像将被用来揭示俯冲驱动的地幔流的性质，它如何与板块规模的流动，以及它如何响应正常和斜收敛。 将记录地壳物理性质的变化，以及这些变化是否与沿阿拉斯加-阿留申俯冲带沿着的地震耦合变化相一致，从而导致大逆冲断层地震的倾向或缺乏。将使用新的方法，包括三个台站的直接波地震干涉测量法，这种方法可以在没有同时部署的台站之间进行台站间测量;倾斜横向六边形各向异性，这种方法可以更完整地描述地震各向异性，而不限于方位各向异性和视径向各向异性;联合反演海底柔度和面波频散，提供对最上层地壳的剪切速度约束，这是地震成因的一个重要因素。由此产生的模型将阐明岩石圈的各向同性和各向异性的属性，是阿拉斯加和上覆地壳和地幔楔下推力，帮助量化的物理性质和俯冲带的过程。这个奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

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.