Crustal S‐wave velocity structure of the Main Ethiopian Rift from ambient noise tomography
Crustal S‐wave velocity structure of the Main Ethiopian Rift from ambient noise tomography
复制标题
环境噪声断层扫描显示埃塞俄比亚主裂谷的地壳 S 波速度结构
DOI：
10.1111/j.1365-246x.2012.05664.x
复制
发表时间：
2012
影响因子：
2.8
通讯作者：
T. Kang
中科院分区：
文献类型：
--
作者：
Seongryong Kim;A. Nyblade;J. Rhie;C. Baag;T. Kang
摘要
环境噪声层析成像已被用于构建覆盖埃塞俄比亚主要裂谷(MER)北部(NMER)、中部(CMER)和南部(SMER)部分的瑞利波群速度图。此外，还对从群速度图中提取的频散曲线进行了反演，得到了地壳剪切波速度的准三维模型。与埃塞俄比亚高原的地壳结构相比较，我们发现：(1)耶勒-图卢韦尔火山构造线以下所有地壳深度的剪切波速度较低；(2)上地壳深度(<；(3)在Wonji断裂带(WFB)、Nmer和CMER之间的过渡区以及CMER西侧的Silti-Debre Zeit断裂带(SDFZ)之下，(4)Nmer和CMER之间的中地壳深度速度模式与博鲁-托鲁构造高压(BTSH)重合的中地壳深度的偏移量，以及(5)在SMER之下的中或下地壳深度几乎没有低剪切波速度的证据。我们将这些发现主要归因于新生代引起的地壳成分、熔体含量和热结构的沿走向变化，以及在上地壳深度(<；10公里)，与盆地结构和充填有关。我们的发现证实了MER的岩浆管道模型，该模型显示了两个主要的岩浆活动区，一个在WFB下面，另一个在SDFZ下面。模型中的横波速度谱与地震活动深度、上地幔地震异常和地震各向异性具有很好的相关性，如果横波速度沿走向的变化反映了地壳的热结构和成分结构，那么就可以预期到这一点。
SUMMARY
Ambient noise tomography has been used to construct Rayleigh-wave group velocity maps covering the northern (NMER), central (CMER) and southern (SMER) parts of the Main Ethiopian Rift (MER). In addition, dispersion curves, extracted from the group velocity maps, have been inverted to obtain a quasi-3-D model of crustal shear wave velocities. In comparison to crustal structure on the Ethiopian Plateau, we find (1) lower shear wave velocities at all crustal depths beneath the Yerer-Tullu Wellel Volcanotectonic Lineament, (2) lower shear wave velocities throughout the MER at upper crustal depths (<10 km), (3) regions of lower shear wave velocities at mid- (10–20 km) crustal depths beneath the Wonji Fault Belt (WFB), in the transition between the NMER and CMER, and beneath the Silti-Debre zeit Fault Zone (SDFZ) on the western side of the CMER, (4) an offset in the velocity pattern at mid-crustal depths between the NMER and CMER coincident with the Boru-Toru Structural High (BTSH) and (5) little evidence for lower shear wave velocities at mid- or lower-crustal depths beneath the SMER. We attribute these findings primarily to along-strike changes in crustal composition, melt content and thermal structure resulting from the Cenozoic to recent magmatism, and also, at upper crustal depths (<10 km), to basin structure and fill. Our findings corroborate a magmatic plumbing model for the MER that shows two major zones of magmatic activity, one beneath the WFB and the other beneath the SDFZ. The shear wave velocity patterns in our model show good correlation with the depth extent of seismicity, upper-mantle seismic anomalies and seismic anisotropy, as would be expected if the along-strike changes in shear wave velocity reflect the thermal and compositional structure of the crust.
影响因子：
18.3
作者：
Bastow, Ian D.;Keir, Derek
通讯作者：
Keir, Derek