Relationships Between Lithospheric Structures and Rifting in the East African Rift System: A Rayleigh Wave Tomography Study
Relationships Between Lithospheric Structures and Rifting in the East African Rift System: A Rayleigh Wave Tomography Study
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东非裂谷系统岩石圈结构与裂谷作用之间的关系：瑞利波层析成像研究
DOI：
10.1029/2018gc007750
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发表时间：
2018
期刊：
影响因子：
3.7
通讯作者：
N. Accardo
中科院分区：
文献类型：
--
作者：
A. Adams;J. Miller;N. Accardo
东非裂谷系统(EARS)为探索影响大陆裂谷发育和成熟的因素提供了独特的位置。特别是，新生代裂谷和前寒武纪岩石圈结构之间的地理关系表明，这种先前存在的结构对早期裂谷的几何形状和行为产生了影响。本研究利用S 20~100时的瑞雷波相速度，研究了中、南耳裂谷段岩石圈结构和既有构造的横向变异性。该模型是利用1994年至2015年间非同步地震台网的235个台站组成的复合台网记录的789次地震记录构建的。在中耳，我们观察到坦桑尼亚克拉通下方的快速速度，沿着西裂谷分支的孤立的低速区域，以及东裂谷分支所有已解决部分的低速，这与以前的区域面波研究一致。在坦桑尼亚克拉通南部，我们观察到从坦桑尼亚散布带向东南和西南方向的线状低速带，表明东裂谷分支向南分叉。在西裂谷分支的南部，马拉维裂谷与与邦威鲁地块和伊鲁米德带有关的快速运动接壤。这些地区异常快速的速度持续了很长时间，证实了先前研究推断的克拉通岩石圈的存在。在伊鲁米德带下观察到的快速速度延伸到马拉维裂谷的最南端，这表明该地区强大的岩石圈可能会阻碍裂谷的向南传播。
The East African Rift System (EARS) provides a unique location for exploring factors influencing the development and maturation of continental rifting. In particular, the geographical relationships between Cenozoic rifts and Pre‐Cambrian lithospheric structures suggest that such preexisting structures exert an influence on early‐stage rift geometry and behavior. This study uses Rayleigh wave phase velocity at periods of 20 to 100 s to study lateral variability in the lithospheric structures of rift segments and preexisting structures in the central and southern EARS. The model is constructed using records of 789 earthquakes, recorded by a composite station array of 235 stations from nonconcurrent seismic networks between 1994 and 2015. In the central EARS, we observe fast velocities beneath the Tanzania Craton, isolated low‐velocity regions along the Western Rift Branch, and low velocities in all resolved portions of the Eastern Rift Branch, consistent with previous regional surface wave studies. South of the Tanzania Craton, we observe linear low‐velocity zones trending both southeast and southwest from the Tanzania Divergence Zone, suggesting a southern bifurcation of the Eastern Rift Branch. In the southern portions of the Western Rift Branch, the Malawi Rift borders fast velocities associated with the Bangweulu Block and Irumide Belt. Anomalously fast velocities in these regions persist to long periods, confirming the existence of cratonic lithosphere inferred from previous studies. Fast velocities observed beneath the Irumide Belt extend across the southernmost portion of the Malawi Rift, suggesting that strong lithosphere in this region may hinder the southern propagation of the rift.
影响因子：
3.5
作者：
S. Fishwick
通讯作者：
S. Fishwick