Anomalous azimuthal variations with 360° periodicity of Rayleigh phase velocities observed in Scandinavia
Anomalous azimuthal variations with 360° periodicity of Rayleigh phase velocities observed in Scandinavia
复制标题
斯堪的纳维亚半岛观测到的瑞利相速度 360° 周期性的异常方位角变化
DOI：
10.1093/gji/ggaa553
复制
发表时间：
2021
影响因子：
2.8
通讯作者：
Tilmann
中科院分区：
文献类型：
--
作者：
Mauerberger;Maupin;Gudmundsson;Tilmann
我们使用最近部署的ScanArray网络的宽带站覆盖挪威和瑞典的大部分地区，以及芬兰的部分地区，分析瑞利波在斯堪的纳维亚半岛的传播。应用阵列波束形成技术，从ScanArray和永久站在研究区域，共159个站的典型站的距离约为70公里，我们获得相速度为三个子区域，这共同涵盖了大部分斯堪的纳维亚半岛（不包括挪威南部）的记录。所有三个分区的平均相频散曲线相似。他们类似于分散以前观察到的南波罗的海克拉通和约1%，比北波罗的海盾相速度为40和80秒之间的时期。然而，在周期>35 s时，观测到sin（1θ）相速度随方位角的显著变化，最大和最小速度之间的偏差为5%，大于平均速度的总体横向变化。这种变化，这是不兼容的地震各向异性，发生在斯堪的纳维亚半岛的北方和挪威/瑞典南部，但不是在中央研究区。分别在120°和300°的后方位角测量最大和最小速度。这些方向是垂直于一个步骤，在岩石圈软流圈边界（LAB）推断在挪威南部/瑞典以前的研究，这表明大岩石圈异质性的关系。为了检验这一假设，我们进行了2-D的全波形模拟瑞利波传播的合成模型，其中包括一个陡峭的梯度在LAB结合一个显着的减少剪切速度低于LAB。这种设置再现的意见定性，并导致在更高的相速度传播的方向变浅LAB，和较低的传播方向加深LAB，可能是由于前向散射和反射的表面波能量的干扰的基本模式。因此，岩石圈厚度的减少向南挪威在南部，向北大西洋提供了一个合理的解释所观察到的方位角的变化。
We use the recently deployed ScanArray network of broad-band stations covering most of Norway and Sweden as well as parts of Finland to analyse the propagation of Rayleigh waves in Scandinavia. Applying an array beamforming technique to teleseismic records from ScanArray and permanent stations in the study region, in total 159 stations with a typical station distance of about 70 km, we obtain phase velocities for three subregions, which collectively cover most of Scandinavia (excluding southern Norway). The average phase dispersion curves are similar for all three subregions. They resemble the dispersion previously observed for the South Baltic craton and are about 1 per cent slower than the North Baltic shield phase velocities for periods between 40 and 80 s. However, a remarkable sin(1θ) phase velocity variation with azimuth is observed for periods >35 s with a 5 per cent deviation between the maximum and minimum velocities, more than the overall lateral variation in average velocity. Such a variation, which is incompatible with seismic anisotropy, occurs in northern Scandinavia and southern Norway/Sweden but not in the central study area. The maximum and minimum velocities were measured for backazimuths of 120° and 300°, respectively. These directions are perpendicular to a step in the lithosphere–asthenosphere boundary (LAB) inferred by previous studies in southern Norway/Sweden, suggesting a relation to large lithospheric heterogeneity. In order to test this hypothesis, we carried out 2-D full-waveform modeling of Rayleigh wave propagation in synthetic models which incorporate a steep gradient in the LAB in combination with a pronounced reduction in the shear velocity below the LAB. This setup reproduces the observations qualitatively, and results in higher phase velocities for propagation in the direction of shallowing LAB, and lower ones for propagation in the direction of deepening LAB, probably due to the interference of forward scattered and reflected surface wave energy with the fundamental mode. Therefore, the reduction in lithospheric thickness towards southern Norway in the south, and towards the Atlantic ocean in the north provide a plausible explanation for the observed azimuthal variations.
登录
查看更多内容
USArray 可移动阵列的到达角异常
影响因子：
5.3
作者：
A. Foster;G. Ekström;V. Hjörleifsdóttir
通讯作者：
V. Hjörleifsdóttir
挪威南部的上地幔结构，来自呈现多路径的瑞利波数据的波束形成
影响因子：
2.8
作者：
V. Maupin
通讯作者：
V. Maupin
通过远震层析成像解析瑞典国家地震台网（SNSN）下方波罗的海地盾的上地幔结构
DOI：
--
发表时间：
2007
期刊：
影响因子：
--
作者：
T. Eken;Z. Shomali;Z. Shomali;R. Roberts;R. Bödvarsson
通讯作者：
R. Bödvarsson
根据 TOR1 项目数据的瑞利波分析推断，整个 Sorgenfrei-Tornquist 带的岩石圈结构形成鲜明对比。
DOI：
--
发表时间：
2002
期刊：
影响因子：
--
作者：
N. Cotte;H. Pedersen
通讯作者：
H. Pedersen
影响因子：
4.2
作者：
Fishwick, S.;Heintz, M.;Yoshizawa, K.
通讯作者：
Yoshizawa, K.