Distributed Extension Across the Ethiopian Rift and Plateau Illuminated by Joint Inversion of Surface Waves and Scattered Body Waves
Distributed Extension Across the Ethiopian Rift and Plateau Illuminated by Joint Inversion of Surface Waves and Scattered Body Waves
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DOI：
10.1029/2021gc010179
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发表时间：
2021-09
期刊：
影响因子：
3.7
通讯作者：
J. Petruska;Z. Eilon
中科院分区：
文献类型：
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作者：
J. Petruska;Z. Eilon
东非裂谷系统提供了一个难得的地点来观察大范围的裂谷状态。埃塞俄比亚主裂谷 (MER) 中明确的活动窄裂谷过渡到早期延伸，最终通过埃塞俄比亚高原 (EP) 的西北侧岩石圈发生预裂谷。尽管 MER 已得到充分研究，但离轴区域受到的关注较少。我们开发了瑞利波相速度图、Ps 接收器函数和 H-κ 叠加表面，并使用跨维、分层贝叶斯反演算法联合反演这些数据，以创建跨 MER 和 EP 的剪切速度剖面。观察到的所有剪切速度均低于 PREM 全球平均速度，这反映了羽流冲击持续升高的温度。在 EP 中，我们发现了一条与 MER 轴平行的浅地幔慢剪切速度线状结构，其中剪切速度较快。 MER 的地壳很浅，EP 的最西北侧翼也是如此。整个高原其他地方发现的较厚的地壳是由地壳底侵和溢流玄武岩侵位造成的。剪切速度比已经很低的区域平均速度降低得更多，与地表火山特征、大地测量观测以及缓慢的纵波和横波异常相一致，支持埃塞俄比亚高原的离轴延伸，需要重新评估狭窄的中东欧大陆破裂的定位。
The East African Rift System provides a rare location in which to observe a wide scope of rifting states. Well‐defined active narrow rifting in the Main Ethiopian Rift (MER) transitions to incipient extension and eventually pre‐rifted lithosphere through the northwestern flank of the Ethiopian Plateau (EP). Although the MER is well studied, the off‐axis region has received less attention. We develop Rayleigh wave phase velocity maps, Ps receiver functions, and H‐κ stack surfaces, and jointly invert these data using a trans‐dimensional, hierarchical Bayesian inversion algorithm to create shear velocity profiles across the MER and EP. All shear velocities observed are slower than the PREM global average, a reflection of the elevated temperatures that persist from plume impingement. In the EP, we find a shallow mantle slow shear velocity lineament parallel to the MER axis, amidst otherwise faster shear velocities. The crust is shallow in the MER, and also in the northwestern‐most EP flank. Thicker crust found elsewhere throughout the plateau is caused by crustal underplating and flood basalt emplacement. Shear velocities more reduced than the already low regional average, in concert with surficial volcanic features, geodetic observations, and slow P‐ and S‐wave anomalies, support off‐axis extension in the Ethiopian plateau, requiring reevaluation of the localization of continental breakup in the narrow MER.