当前位置: X-MOL 学术Geophys. J. Int. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Evidence for radial anisotropy in the lower crust of the Apennines from Bayesian ambient noise tomography in Europe
Geophysical Journal International ( IF 2.8 ) Pub Date : 2021-02-19 , DOI: 10.1093/gji/ggab066
C Alder 1 , E Debayle 1 , T Bodin 1 , A Paul 2 , L Stehly 2 , H Pedersen 2 ,
Affiliation  

Probing seismic anisotropy of the lithosphere provides valuable clues on the fabric of rocks. We present a 3-D probabilistic model of shear wave velocity and radial anisotropy of the crust and uppermost mantle of Europe, focusing on the mountain belts of the Alps and Apennines. The model is built from Love and Rayleigh dispersion curves in the period range 5–149 s. Data are extracted from seismic ambient noise recorded at 1521 broad-band stations, including the AlpArray network. The dispersion curves are first combined in a linearized least squares inversion to obtain 2-D maps of group velocity at each period. Love and Rayleigh maps are then jointly inverted at depth for shear wave velocity and radial anisotropy using a Bayesian Monte Carlo scheme that accounts for the trade-off between radial anisotropy and horizontal layering. The isotropic part of our model is consistent with previous studies. However, our anisotropy maps differ from previous large scale studies that suggested the presence of significant radial anisotropy everywhere in the European crust and shallow upper mantle. We observe instead that radial anisotropy is mostly localized beneath the Apennines while most of the remaining European crust and shallow upper mantle is isotropic. We attribute this difference to trade-offs between radial anisotropy and thin (hectometric) layering in previous studies based on least-squares inversions and long period data (>30 s). In contrast, our approach involves a massive data set of short period measurements and a Bayesian inversion that accounts for thin layering. The positive radial anisotropy (VSH > VSV) observed in the lower crust of the Apennines cannot result from thin layering. We rather attribute it to ductile horizontal flow in response to the recent and present-day extension in the region.

中文翻译:

欧洲贝叶斯环境噪声层析成像技术对亚平宁山脉下地壳径向各向异性的证据

探测岩石圈的地震各向异性为岩石构造提供了有价值的线索。我们介绍了欧洲地壳和最上层地幔的剪切波速度和径向各向异性的3-D概率模型,重点是阿尔卑斯山和亚平宁山脉。该模型是根据5–149 s范围内的Love和Rayleigh色散曲线建立的。数据是从1521个宽带站(包括AlpArray网络)记录的地震环境噪声中提取的。首先在线性最小二乘反演中组合色散曲线,以获得每个周期的群速度的二维图。然后,使用贝叶斯蒙特卡洛方案在深度上联合反转Love和Rayleigh映射图,以实现剪切波速度和径向各向异性,该方法考虑了径向各向异性和水平分层之间的折衷。我们模型的各向同性部分与以前的研究一致。但是,我们的各向异性图与以前的大规模研究不同,后者表明欧洲地壳和浅上地幔到处都存在明显的径向各向异性。相反,我们观察到径向各向异性主要局限在亚平宁山脉之下,而其余大部分的欧洲地壳和浅上地幔是各向同性的。我们将这种差异归因于先前研究中基于最小二乘反演和长期数据(> 30 s)的径向各向异性和薄(厚)层之间的权衡。相比之下,我们的方法涉及短期测量的大量数据集和解释薄层的贝叶斯反演。正径向各向异性(我们的各向异性图与以前的大规模研究不同,后者表明欧洲地壳和浅地幔中到处都存在明显的径向各向异性。相反,我们观察到径向各向异性主要局限在亚平宁山脉之下,而其余大部分的欧洲地壳和浅上地幔是各向同性的。我们将这种差异归因于先前研究中基于最小二乘反演和长期数据(> 30 s)的径向各向异性和薄(厚)层之间的权衡。相比之下,我们的方法涉及短期测量的大量数据集和解释薄层的贝叶斯反演。正径向各向异性(我们的各向异性图与以前的大规模研究不同,后者表明欧洲地壳和浅地幔中到处都存在明显的径向各向异性。相反,我们观察到径向各向异性主要局限在亚平宁山脉之下,而其余大部分的欧洲地壳和浅上地幔是各向同性的。我们将这种差异归因于先前研究中基于最小二乘反演和长期数据(> 30 s)的径向各向异性和薄(厚)层之间的权衡。相比之下,我们的方法涉及短期测量的大量数据集和解释薄层的贝叶斯反演。正径向各向异性(相反,我们观察到径向各向异性主要局限在亚平宁山脉之下,而其余大部分的欧洲地壳和浅上地幔是各向同性的。我们将这种差异归因于先前研究中基于最小二乘反演和长期数据(> 30 s)的径向各向异性和薄(厚)层之间的权衡。相比之下,我们的方法涉及短期测量的大量数据集和解释薄层的贝叶斯反演。正径向各向异性(相反,我们观察到径向各向异性主要局限在亚平宁山脉之下,而其余大部分的欧洲地壳和浅上地幔是各向同性的。我们将这种差异归因于先前研究中基于最小二乘反演和长期数据(> 30 s)的径向各向异性和薄(厚)层之间的权衡。相比之下,我们的方法涉及短期测量的大量数据集和解释薄层的贝叶斯反演。正径向各向异性(我们的方法涉及大量的短期测量数据集和贝叶斯反演,这说明了薄层。正径向各向异性(我们的方法涉及大量的短期测量数据集和贝叶斯反演,这说明了薄层。正径向各向异性(在亚平宁山脉下部地壳中观察到的V SH > V SV)不能由薄层形成。我们宁愿将其归因于该区域最近和当前扩展的延性水平流。
更新日期:2021-02-19
down
wechat
bug