Surface Wave Isotropic and Azimuthally Anisotropic Dispersion Across Alaska and the Alaska‐Aleutian Subduction Zone
Surface Wave Isotropic and Azimuthally Anisotropic Dispersion Across Alaska and the Alaska‐Aleutian Subduction Zone
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DOI：
10.1029/2022jb024885
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发表时间：
2022-11
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影响因子：
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通讯作者：
Chuanming Liu;Shane Zhang;A. Sheehan;M. Ritzwoller
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文献类型：
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作者：
Chuanming Liu;Shane Zhang;A. Sheehan;M. Ritzwoller
需要对阿拉斯加和阿留申俯冲带的表面波各向异性进行全面观测，以提高对其构造、地幔动力学和地震风险的了解。我们利用 USArray 可移动阵列和阿拉斯加区域网络以及阿拉斯加-阿留申俯冲带陆上和海上的阿拉斯加两栖社区地震实验站进行此类观测。我们的数据包括地震的瑞利波和洛夫波相位色散（28-85 秒）以及环境噪声双站和三站干涉测量（8-50 秒）。与单独使用双站干涉测量相比，三站干涉测量显着提高了信噪比，并且保留的测量数量大约增加了一倍。由不同方法构建的各向同性和各向异性断层扫描图之间的平均差异位于其不确定性之内，这是组合测量结果的理由。复合层析图包括陆上和海上8~85 s的瑞利波各向同性和方位各向异性，以及8~80 s的陆上Love波各向异性。在阿拉斯加-阿留申俯冲带，瑞利波快方向随着周期的增加从海沟平行变为垂直，再回到平行，显然反映了俯冲太平洋板块的影响。层析成像图为推断阿拉斯加和阿留申俯冲带的 3D 各向异性地壳和上地幔结构提供了基础。
Comprehensive observations of surface wave anisotropy across Alaska and the Aleutian subduction zone are needed to improve understanding of its tectonics, mantle dynamics, and earthquake risk. We produce such observations, using stations from the USArray Transportable Array and regional networks across Alaska and the Alaska Amphibious Community Seismic Experiment in the Alaska‐Aleutian subduction zone both onshore and offshore. Our data include Rayleigh and Love wave phase dispersion from earthquakes (28–85 s) and ambient noise two‐ and three‐station interferometry (8–50 s). Compared with using two‐station interferometry alone, three‐station interferometry significantly improves the signal‐to‐noise ratio and approximately doubles the number of measurements retained. Average differences between both isotropic and anisotropic tomographic maps constructed from different methods lie within their uncertainties, which is justification for combining the measurements. The composite tomographic maps include Rayleigh wave isotropy and azimuthal anisotropy from 8 to 85 s both onshore and offshore, and onshore Love wave isotropy from 8 to 80 s. In the Alaska‐Aleutian subduction zone, Rayleigh wave fast directions vary from trench parallel to perpendicular and back to parallel with increasing periods, apparently reflecting the effect of the subducted Pacific Plate. The tomographic maps provide a basis for inferring the 3‐D anisotropic crustal and uppermost mantle structure across Alaska and the Aleutian subduction zone.