A 3‐D Shear Velocity Model of the Crust and Uppermost Mantle Beneath Alaska Including Apparent Radial Anisotropy
A 3‐D Shear Velocity Model of the Crust and Uppermost Mantle Beneath Alaska Including Apparent Radial Anisotropy
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DOI：
10.1029/2019jb018122
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发表时间：
2019-10
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影响因子：
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通讯作者：
Lili Feng;M. Ritzwoller
中科院分区：
文献类型：
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作者：
Lili Feng;M. Ritzwoller
本文基于500多个宽带台站记录的地震数据，在~50 km网格上，给出了阿拉斯加及其周围地区地壳和上地幔的三维剪切速度结构模型，包括地壳和地幔径向各向异性。该模型来自瑞利波群和相速度和Love波相速度从环境噪声和地震数据确定的贝叶斯蒙特卡罗反演。在模型中解决的突出特征包括：（1）在阿拉斯加中部和北方的部分地区，在白垩纪受到显着的伸展明显的地壳径向各向异性是最强的。这是一致的地壳各向异性所造成的变形对齐中，下地壳片硅酸盐（云母）与浅倾斜面理平面下方的伸展域。(2)地壳厚度估计值与米勒和莫雷西（2018，https：//doi.org/10.1785/0220180222）的接收器函数相似。(3)北极-阿拉斯加的岩石圈非常厚，剪切波速度至少延伸到120公里的深度，这可能会对该地区演化的旋转传输模型提出挑战。(4)阿拉斯加下方的俯冲岩石圈得到解决，包括我们称之为“巴伦岛板异常”，一个“东亚板边缘”的德纳里火山口，“兰格利亚板异常”，和雅库塔特岩石圈俯冲向海的兰格尔火山场。(5)阿拉斯加俯冲带的几何形状与Jadamec和Billen（2010，https：//doi.org/10.1038/nature09053）的板片模型Alaska_3D 1.0基本一致，除了雅库塔特“板肩区”，这是我们模型中新成像的。
This paper presents a model of the 3‐D shear velocity structure of the crust and uppermost mantle beneath Alaska and its surroundings on a ~50‐km grid, including crustal and mantle radial anisotropy, based on seismic data recorded at more than 500 broadband stations. The model derives from a Bayesian Monte Carlo inversion of Rayleigh wave group and phase speeds and Love wave phase speeds determined from ambient noise and earthquake data. Prominent features resolved in the model include the following: (1) Apparent crustal radial anisotropy is strongest across the parts of central and northern Alaska that were subjected to significant extension during the Cretaceous. This is consistent with crustal anisotropy being caused by deformationally aligned middle to lower crustal sheet silicates (micas) with shallowly dipping foliation planes beneath extensional domains. (2) Crustal thickness estimates are similar to those from receiver functions by Miller and Moresi (2018, https://doi.org/10.1785/0220180222). (3) Very thick lithosphere underlies Arctic‐Alaska, with high shear wave speeds that extend at least to 120‐km depth, which may challenge rotational transport models for the evolution of the region. (4) Subducting lithosphere beneath Alaska is resolved, including what we call the “Barren Islands slab anomaly,” an “aseismic slab edge” north of the Denali Volcanic Gap, the “Wrangellia slab anomaly,” and Yakutat lithosphere subducting seaward of the Wrangell volcanic field. (5) The geometry of the Alaskan subduction zone generally agrees with the slab model Alaska_3D 1.0 of Jadamec and Billen (2010, https://doi.org/10.1038/nature09053) except for the Yakutat “slab shoulder region,” which is newly imaged in our model.