Kumar Utpal, Legendre Cédric P
Berkeley Seismological Laboratory, University of California, Berkeley, 307 McCone Hall #4760, Berkeley, CA, 94720-4760, USA.
Institute of Geophysics, Czech Academy of Science, Boční II/1401, 14131, Praha, Czech Republic.
Sci Rep. 2022 Oct 11;12(1):17036. doi: 10.1038/s41598-022-20890-5.
The Afar triple junction accustoms the diverging plate dynamics between the Arabian, Nubian, and Somalian plates along the Red Sea, Gulf of Aden, and East African rifts. The average anisotropy obtained from shear-wave splitting measurements agrees with the surface motion recovered by geodetic analyses. However, the vertical layering of anisotropy in this region is yet to be accurately determined. Here, we use earthquake seismic data to map Rayleigh-wave azimuthal anisotropy in the crust and lithospheric mantle beneath the East African Rift System. Our results suggest that a layering of anisotropy is present around the East African Rift System. At shorter periods that sample the crust, rift-parallel anisotropy is present in the vicinity of the rift, but in the central part of the rift, rift-normal anisotropy is found. At longer periods, sampling the lithospheric mantle, the anisotropic pattern is quite different. These observations suggest that the crust and lithospheric mantle are mechanically decoupled beneath the environs of the East African Rift System. Similarly, these results suggest complex dynamics within the crust and lithosphere in the region of the Afar triple junction.
阿法尔三联点调节着阿拉伯板块、努比亚板块和索马里板块之间沿红海、亚丁湾和东非裂谷的离散板块动力学。通过剪切波分裂测量获得的平均各向异性与大地测量分析恢复的地表运动一致。然而，该区域各向异性的垂直分层尚未得到准确确定。在这里，我们使用地震数据绘制东非裂谷系统下方地壳和岩石圈地幔中的瑞利波方位各向异性图。我们的结果表明，东非裂谷系统周围存在各向异性分层。在较短周期（采样地壳）时，裂谷附近存在与裂谷平行的各向异性，但在裂谷中部发现了与裂谷垂直的各向异性。在较长周期（采样岩石圈地幔）时，各向异性模式有很大不同。这些观测结果表明，东非裂谷系统周边下方的地壳和岩石圈地幔在力学上是解耦的。同样，这些结果表明阿法尔三联点区域内地壳和岩石圈内部存在复杂的动力学。
