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The magma-assisted removal of Arabia in Afar: Evidence from dike injection in the Ethiopian rift captured using InSAR and seismicity

The magma-assisted removal of Arabia in Afar: Evidence from dike injection in the Ethiopian rift captured using InSAR and seismicity
The magma-assisted removal of Arabia in Afar: Evidence from dike injection in the Ethiopian rift captured using InSAR and seismicity
In seismically and tectonically active regions, the present-day strain field tends to bias interpretation of the geological record. This is usually reasonable, but in areas such as triple junctions, the orientation of stress and the locus of strain can evolve abruptly in space and time. We present deformation measurements using satellite radar interferometry (InSAR) and seismicity that together capture the intrusion of a ~6 km long, ~1.5 m wide dike into the upper crust of the Ethiopian rift in southern Afar during May 2000. Dike-induced volcano-tectonic seismicity suggests that the intrusion was injected laterally during a period of ~4 days. Seismic moment release accounts for only 5% of the total 1.6 × 1018 Nm geodetic moment, showing that diking accommodates the majority of strain. The intrusion intriguingly strikes at N122°E, perpendicular to the trend of the present-day East African rift. The geometry and age constraints on faulting and volcanic activity in southern Afar, combined with plate reconstructions, suggest that the dike likely intrudes an ~ESE-SE striking magmatic system that localized strain during Oligo-Miocene rifting in the Red Sea and Gulf of Aden. We also identify the southerly extent of the Arabian Plate in Afar during the Oligocene in mantle seismic tomographic images: an abrupt increase in seismic velocity in southern Afar is coincident with a stepped increase of ~20 Myr in the time elapsed since the onset of plate stretching. The anomalous orientation of the May 2000 intrusion implies that African-Arabian tectonics still influences the stress field in southern Afar and is at least partly accommodated by magma intrusion.
0278-7407
TC2008
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Pagli, Carolina
290edb22-712b-4563-a868-af4c21fdb6b0
Bastow, Ian D.
7a2698d0-d535-4462-a9a9-0e3293d2d667
Ayele, Atalay
5b4eeb35-d229-4325-8940-d934dab7563d
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Pagli, Carolina
290edb22-712b-4563-a868-af4c21fdb6b0
Bastow, Ian D.
7a2698d0-d535-4462-a9a9-0e3293d2d667
Ayele, Atalay
5b4eeb35-d229-4325-8940-d934dab7563d

Keir, Derek, Pagli, Carolina, Bastow, Ian D. and Ayele, Atalay (2011) The magma-assisted removal of Arabia in Afar: Evidence from dike injection in the Ethiopian rift captured using InSAR and seismicity. Tectonics, 30 (2), TC2008. (doi:10.1029/2010TC002785).

Record type: Article

Abstract

In seismically and tectonically active regions, the present-day strain field tends to bias interpretation of the geological record. This is usually reasonable, but in areas such as triple junctions, the orientation of stress and the locus of strain can evolve abruptly in space and time. We present deformation measurements using satellite radar interferometry (InSAR) and seismicity that together capture the intrusion of a ~6 km long, ~1.5 m wide dike into the upper crust of the Ethiopian rift in southern Afar during May 2000. Dike-induced volcano-tectonic seismicity suggests that the intrusion was injected laterally during a period of ~4 days. Seismic moment release accounts for only 5% of the total 1.6 × 1018 Nm geodetic moment, showing that diking accommodates the majority of strain. The intrusion intriguingly strikes at N122°E, perpendicular to the trend of the present-day East African rift. The geometry and age constraints on faulting and volcanic activity in southern Afar, combined with plate reconstructions, suggest that the dike likely intrudes an ~ESE-SE striking magmatic system that localized strain during Oligo-Miocene rifting in the Red Sea and Gulf of Aden. We also identify the southerly extent of the Arabian Plate in Afar during the Oligocene in mantle seismic tomographic images: an abrupt increase in seismic velocity in southern Afar is coincident with a stepped increase of ~20 Myr in the time elapsed since the onset of plate stretching. The anomalous orientation of the May 2000 intrusion implies that African-Arabian tectonics still influences the stress field in southern Afar and is at least partly accommodated by magma intrusion.

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Published date: 2011

Identifiers

Local EPrints ID: 180755
URI: http://eprints.soton.ac.uk/id/eprint/180755
ISSN: 0278-7407
PURE UUID: b5ba44fd-2143-4aaa-a420-bf65bb9df96c
ORCID for Derek Keir: ORCID iD orcid.org/0000-0001-8787-8446

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Date deposited: 11 Apr 2011 13:12
Last modified: 09 Nov 2021 03:24

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Contributors

Author: Derek Keir ORCID iD
Author: Carolina Pagli
Author: Ian D. Bastow
Author: Atalay Ayele

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