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首页> 外文期刊>South African Journal of Geology: Being the Transaction of the Geological Society of South African: Syndie die Verhandelinge van die Geologiese Vereniging van Suid-Afrika >S-WAVE VELOCITY STRUCTURE OF THE CRUST AND UPPER MANTLE BENEATH KENYA IN COMPARISON TO TANZANIA AND ETHIOPIA: IMPLICATIONS FOR THE FORMATION OF THE EAST AFRICAN AND ETHIOPIAN PLATEAUS
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S-WAVE VELOCITY STRUCTURE OF THE CRUST AND UPPER MANTLE BENEATH KENYA IN COMPARISON TO TANZANIA AND ETHIOPIA: IMPLICATIONS FOR THE FORMATION OF THE EAST AFRICAN AND ETHIOPIAN PLATEAUS

机译：肯尼亚与肯尼亚和埃塞俄比亚相比，地壳和上地幔的S波速度结构：对东非和埃塞俄比亚高原形成的影响

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摘要

New estimates of the S-wave velocity structure of the crust and upper mantle beneath the Kenya Rift and surrounding Kenya Highlands have been obtained by jointly inverting P wave receiver functions and Rayleigh wave phase and group velocities. The joint inversion was performed for seven broadband seismic stations, five that were part of the Kenya broadband seismic experiment and two belonging to the Global Seismic Network. 1-D S-wave velocity models obtained from the inversions have been compared to similar models for Tanzania and Ethiopia to identify differences in lithospheric structure beneath the East African and Ethiopian Plateaus. The S-wave velocity structure of the upper mantle to at least 100 to 150 km depth beneath the Kenya Highlands is similar to structure under the East African Plateau in Tanzania. It therefore appears that the plateau lithosphere under the Kenya Highlands has not been affected thermally to any greater extent than the plateau lithosphere beneath Tanzania. Under the Kenya Rift, however, the lithosphere has been substantially modified. S-wave velocities at depths of 80 to 150 km beneath the rift are 8 to 10% lower compared to under the Kenya Highlands, which may be a sufficiently large change to indicate the presence of partial melt. There is little similarity between the plateau lithosphere in East Africa and Ethiopia. The lithosphere under the Ethiopian Plateau is thin, extending to a depth of no more than about 80 to 90 km depth, compared to 100 to 150 km beneath Tanzania and the Kenya Highlands. The maximum S-wave velocity in the lithosphere is also very low, reaching only to 4.2 to 4.3 km/s, compared to 4.6 to 4.7 km/s beneath Tanzania and the Kenya Highlands. These differences indicate that the buoyant support for the plateau elevation in East Africa, including the Kenya Highlands, resides at deeper depths in the mantle than beneath the Ethiopian Plateau.
机译：通过联合反演P波接收器函数以及瑞利波相速度和群速度，已经获得了对肯尼亚裂谷和周围肯尼亚高地以下地壳和上地幔S波速度结构的新估计。对七个宽带地震台站进行了联合反演，其中五个是肯尼亚宽带地震实验的一部分，另外两个属于全球地震台网。从反演中获得的一维S波速度模型已经与坦桑尼亚和埃塞俄比亚的类似模型进行了比较，以确定东非和埃塞俄比亚高原下方岩石圈结构的差异。肯尼亚高地以下至少100至150 km深度的上地幔的S波速度结构类似于坦桑尼亚东非高原的结构。因此，似乎肯尼亚高地以下的高原岩石圈没有受到比坦桑尼亚以下的高原岩石圈更大的热影响。然而，在肯尼亚大裂谷之下，岩石圈已作了重大修改。与肯尼亚高地相比，裂谷下方80至150 km深度的S波速度要低8％至10％，这可能是一个足够大的变化，表明存在部分融化。东非高原岩石圈和埃塞俄比亚之间几乎没有相似之处。埃塞俄比亚高原下的岩石圈很薄，延伸到不超过约80至90 km的深度，而坦桑尼亚和肯尼亚高地以下则为100至150 km。岩石圈中的最大S波速度也非常低，仅达到4.2至4.3 km / s，而坦桑尼亚和肯尼亚高地以下则为4.6至4.7 km / s。这些差异表明，包括肯尼亚高地在内的东非高原海拔的活跃支撑位于地幔中比埃塞俄比亚高原更深的深度。

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