Left-lateral transtension along the Ethiopian Rift and constrains on the mantle-reference plate motions
Left-lateral transtension along the Ethiopian Rift and constrains on the mantle-reference plate motions
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沿埃塞俄比亚裂谷的左旋张量及其对地幔参考板块运动的约束
DOI：
10.1016/j.tecto.2014.05.036
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发表时间：
2014
期刊：
影响因子：
2.9
通讯作者：
C. Doglioni
中科院分区：
文献类型：
--
作者：
A. Muluneh;M. Cuffaro;C. Doglioni
我们通过大地测量速度、震源机制反演、结构数据分析和地质剖面的汇编，介绍了东非裂谷系统北部埃塞俄比亚裂谷的运动学。在埃塞俄比亚裂谷中部，GPS速度场显示出ENE方向的系统震级增加，地震震源机制和断层滑移反演记录的增量伸展应变轴显示出≈N100°E方向。 GPS 速度矢量方向与增量拉伸应变方向之间的偏差是由于沿裂谷 NE-SW 走向段的左侧转拉变形而产生的。这种解释与张性断层和转张性断层的雁行模式、火山中心的分布以及裂谷本身的不对称性是一致的。我们还分析了埃塞俄比亚裂谷相对于地幔的运动学，比较了深部和浅部热点参考系中的结果。虽然裂谷的倾斜方向是由预先存在的岩石圈结构控制的，但这两个参考系预测了非洲和索马里板块沿着裂谷本身的不同运动学，无论是在大小和方向上，还是相对于地幔而言。然而，与在浅层热点框架中观察到的索马里相比，观察到的沿裂谷的运动学和构造更符合非洲更快的西西向运动。非洲相对于索马里板块的西西向运动较快，推测是由于非洲下方软流圈顶部（LVZ——低速区）的粘度较低。这些发现对于张拉背景下大陆裂谷的演化具有重要意义，并为地幔参考系中非洲-索马里板块相互作用背景下埃塞俄比亚裂谷的运动学提供了证据。
We present the kinematics of the Ethiopian Rift, in the northern part of East African Rift System, derived from compilation of geodetic velocities, focal mechanism inversions, structural data analysis and geological profiles. In the central Ethiopian Rift, the GPS velocity field shows a systematic magnitude increase in ENE direction, and the incremental extensional strain axes recorded by earthquake focal mechanisms and fault slip inversion show ≈ N100°E orientation. This deviation between direction of GPS velocity vectors and orientation of incremental extensional strain is developed due to left lateral transtensional deformation along the NE–SW trending segment of the rift. This interpretation is consistent with the en-échelon pattern of tensional and transtensional faults, plus the distribution of the volcanic centers, and the asymmetry of the rift itself. We analyzed the kinematics of the Ethiopian Rift also relative to the mantle comparing the results in the deep and shallow hotspot reference frames. While the oblique orientation of the rift was controlled by the pre-existing lithospheric fabric, the two reference frames predict different kinematics of Africa and Somalia plates along the rift itself, both in magnitude and direction, and with respect to the mantle. However, the observed kinematics and tectonics along the rift are more consistent with a faster WSW-ward motion of Africa than Somalia observed in the shallow hotspot framework. The faster WSW motion of Africa with respect to Somalia plate is inferred to be due to the lower viscosity in the top asthenosphere (LVZ—low-velocity zone) beneath Africa. These findings have significant implication for the evolution of continental rifting in transtensional settings and provide evidence for the kinematics of the Ethiopian Rift in the context of the Africa–Somalia plate interaction in the mantle reference frame.
影响因子：
18.3
作者：
C. Rychert;J. Hammond;N. Harmon;J. Kendall;D. Keir;C. Ebinger;I. Bastow;A. Ayele;M. Belachew;G. Stuart
通讯作者：
C. Rychert;J. Hammond;N. Harmon;J. Kendall;D. Keir;C. Ebinger;I. Bastow;A. Ayele;M. Belachew;G. Stuart