Radial Anisotropy and Sediment Thickness of West and Central Antarctica Estimated From Rayleigh and Love Wave Velocities
Radial Anisotropy and Sediment Thickness of West and Central Antarctica Estimated From Rayleigh and Love Wave Velocities
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DOI：
10.1029/2021jb022857
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发表时间：
2022-03
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影响因子：
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通讯作者：
Zheng-Zheng Zhou-Zheng;D. Wiens;W. Shen;R. Aster;A. Nyblade;T. Wilson
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作者：
Zheng-Zheng Zhou-Zheng;D. Wiens;W. Shen;R. Aster;A. Nyblade;T. Wilson
最近许多南极地震结构研究都使用瑞利波数据，因此只能确定 SV 结构。拉夫波为浅层结构提供了更高的分辨率，并且与瑞利波相结合，可以通过比较垂直 (VSV) 和水平 (VSH) 极化剪切速度来约束径向各向异性。在这项研究中，我们联合分析了来自环境噪声的瑞利波和洛夫波相位和群速度，利用过去 20 年在南极洲收集的所有宽带数据，开发了一个新的南极洲西部和中部的径向各向异性速度模型，该模型具有改进的浅地壳分辨率。使用蒙特卡罗方法估计并反演瑞利波和洛夫波的群速度图和相速度图以获得剪切波速度结构。我们确定了一张新的沉积物分布图，该图揭示了东南罗斯海湾下方的厚沉积盆地（约 4 公里）。极地冰下盆地和本特利冰下海沟等内部盆地的沉积物厚度适中（VSV），可能是由于含云母岩石的晶格择优取向所致。然而，中下地壳的大片区域表现出负各向异性，这可能是由于斜长石的晶格择优取向所致。南极洲西部最上地幔的特点是具有强烈的正径向各向异性（4%–8%），在横贯南极洲和惠特莫尔山脉下方各向异性最大，可能是由于构造活动导致水平橄榄石择优取向所致。
Many recent Antarctic seismic structure studies use Rayleigh wave data and thus determine only the SV structure. Love waves provide greater resolution for shallow structure, and coupled with Rayleigh waves, can constrain radial anisotropy by comparing vertically (VSV) and horizontally (VSH) polarized shear velocities. In this study, we jointly analyze Rayleigh and Love wave phase and group velocities from ambient noise to develop a new radially anisotropic velocity model for West and Central Antarctica with an improved shallow crustal resolution using all broadband data collected in Antarctica over the past 20 years. Group and phase velocity maps for Rayleigh and Love waves are estimated and inverted for shear wave velocity structure using a Monte Carlo method. We determine a new sediment distribution map that reveals a thick sedimentary basin (∼4 km) beneath the Southeastern Ross Embayment. Sediment thicknesses at interior basins such as the Polar Subglacial Basin and Bentley Subglacial Trench are modest ( VSV), likely due to lattice preferred orientation of mica‐bearing rocks. However, large regions of the mid‐to‐lower crust show negative anisotropy, likely due to lattice preferred orientation of plagioclase. The uppermost mantle is characterized by strong positive radial anisotropy (4%–8%) in West Antarctica, with the largest anisotropy beneath the Transantarctic and Whitmore Mountains, likely resulting from horizontal olivine preferred orientation due to tectonic activity.