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Mapping the evolving strain field during continental breakup from crustal anisotropy in the Afar Depression

Mapping the evolving strain field during continental breakup from crustal anisotropy in the Afar Depression
Mapping the evolving strain field during continental breakup from crustal anisotropy in the Afar Depression
Rifting of the continents leading to plate rupture occurs by a combination of mechanical deformation and magma intrusion, yet the spatial and temporal scales over which these alternate mechanisms localize extensional strain remain controversial. Here we quantify anisotropy of the upper crust across the volcanically active Afar Triple Junction using shear-wave splitting from local earthquakes to evaluate the distribution and orientation of strain in a region of continental breakup. The pattern of S-wave splitting in Afar is best explained by anisotropy from deformation-related structures, with the dramatic change in splitting parameters into the rift axis from the increased density of dyke-induced faulting combined with a contribution from oriented melt pockets near volcanic centres. The lack of rift-perpendicular anisotropy in the lithosphere, and corroborating geoscientific evidence of extension dominated by dyking, provide strong evidence that magma intrusion achieves the majority of plate opening in this zone of incipient plate rupture.
285
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Belachew, M.
3a0232fd-0c1b-49ad-82a8-9e5aaf1e3cfa
Ebinger, C.J.
aedfe44b-76f6-4882-9522-0079fba9feda
Kendall, J.-M.
7822c57f-b560-447a-9515-ac384337a3b7
Hammond, J.O.S.
df081c77-2e69-4753-8846-549826d905bb
Stuart, G.W.
42655128-f55d-42a7-afd8-7a2fca1c01a3
Ayele, A.
2a0d90e9-a4be-4484-9301-5c4df46f9407
Rowland, J.V.
2202415e-5040-481b-adbd-f567021f4509
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Belachew, M.
3a0232fd-0c1b-49ad-82a8-9e5aaf1e3cfa
Ebinger, C.J.
aedfe44b-76f6-4882-9522-0079fba9feda
Kendall, J.-M.
7822c57f-b560-447a-9515-ac384337a3b7
Hammond, J.O.S.
df081c77-2e69-4753-8846-549826d905bb
Stuart, G.W.
42655128-f55d-42a7-afd8-7a2fca1c01a3
Ayele, A.
2a0d90e9-a4be-4484-9301-5c4df46f9407
Rowland, J.V.
2202415e-5040-481b-adbd-f567021f4509

Keir, Derek, Belachew, M., Ebinger, C.J., Kendall, J.-M., Hammond, J.O.S., Stuart, G.W., Ayele, A. and Rowland, J.V. (2011) Mapping the evolving strain field during continental breakup from crustal anisotropy in the Afar Depression. Nature Communications, 2 (285), 285. (doi:10.1038/ncomms1287).

Record type: Article

Abstract

Rifting of the continents leading to plate rupture occurs by a combination of mechanical deformation and magma intrusion, yet the spatial and temporal scales over which these alternate mechanisms localize extensional strain remain controversial. Here we quantify anisotropy of the upper crust across the volcanically active Afar Triple Junction using shear-wave splitting from local earthquakes to evaluate the distribution and orientation of strain in a region of continental breakup. The pattern of S-wave splitting in Afar is best explained by anisotropy from deformation-related structures, with the dramatic change in splitting parameters into the rift axis from the increased density of dyke-induced faulting combined with a contribution from oriented melt pockets near volcanic centres. The lack of rift-perpendicular anisotropy in the lithosphere, and corroborating geoscientific evidence of extension dominated by dyking, provide strong evidence that magma intrusion achieves the majority of plate opening in this zone of incipient plate rupture.

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More information

Published date: 2011
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 187613
URI: http://eprints.soton.ac.uk/id/eprint/187613
PURE UUID: 455d533b-59f1-4b0f-833f-6442300fe0f7
ORCID for Derek Keir: ORCID iD orcid.org/0000-0001-8787-8446

Catalogue record

Date deposited: 17 May 2011 13:19
Last modified: 17 Dec 2019 01:40

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