Focused Rifting and Magmatism Beneath the Ethiopian Plateau: A Subparallel Zone of Competing Lithospheric Deformation Offset from the Main Ethiopian Rift
Abstract
In Ethiopia, focused deformation within the lithosphere occurs hundreds of kilometers away from the rift valley, evidenced by new shear-wave splitting, receiver function, and body-wave tomography results. Using data from 30 stations on the Ethiopian Plateau, combined with prior data and results from earlier studies, we observe a focused region on the plateau of thickened crust with high Vp/Vs ratio, coincident with rotated seismic anisotropy, and underlain by a pronounced decrease in both Vp and Vs within the lithosphere. At greater depth, the zone of low seismic velocity merges with the low velocity anomaly beneath the dominant rift valley, but the anomaly separates into two distinct fingers at shallower depths. Feeder dikes for pre-rift flood basalt eruptions are mapped in the off-rift perturbed zone, and Quaternary volcanism and extension occur here in the Tana graben. We interpret that this off-rift area was active in the earliest stages of rifting, and remains active today, while extension continues to localize within the Main Ethiopian Rift 400 km to the east. Our results present a snapshot of complex rift evolution, where multiple zones of rifting are active over time but one zone dominates. Focused, active zones of rifting and volcanism within the lithosphere in Ethiopia currently presents a potential analog to understand off-rift structures and deformation along passive margins including eastern North America.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.V24A..05K
- Keywords:
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- 1207 Transient deformation;
- GEODESY AND GRAVITYDE: 9305 Africa;
- GEOGRAPHIC LOCATIONDE: 9604 Cenozoic;
- INFORMATION RELATED TO GEOLOGIC TIMEDE: 8178 Tectonics and magmatism;
- TECTONOPHYSICSDE: 8185 Volcanic arcs;
- TECTONOPHYSICSDE: 8415 Intra-plate processes;
- VOLCANOLOGYDE: 8488 Volcanic hazards and risks;
- VOLCANOLOGYDE: 8499 General or miscellaneous;
- VOLCANOLOGY