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Seismicity during lateral dike propagation: Insights from new data in the recent Manda Hararo–Dabbahu rifting episode (Afar, Ethiopia0

Seismicity during lateral dike propagation: Insights from new data in the recent Manda Hararo–Dabbahu rifting episode (Afar, Ethiopia0
Seismicity during lateral dike propagation: Insights from new data in the recent Manda Hararo–Dabbahu rifting episode (Afar, Ethiopia0
Seismicity released during lateral dike intrusions in the Manda Hararo–Dabbahu Rift (Afar, Ethiopia) provides indirect insight into the distribution and evolution of tensile stress along this magma-assisted divergent plate boundary. In this paper, 5 dike intrusions among the 14 that form the 2005–present rifting episode are analyzed with local and regional seismic data. During dike intrusions, seismicity migrates over distances of 10–15 km at velocities of 0.5–3.0 km/h away from a single reservoir in the center of the rift segment, confirming the analogy with a slow spreading mid-ocean ridge segment. Comparison with geodetic data shows that the reservoir is located 7 km down rift from the topographic summit of the axial depression. Dikes emplaced toward the north are observed to migrate faster and to be more voluminous than those migrating southward, suggesting an asymmetry of tension in the brittle-elastic lithosphere. Seismicity during dike injections is concentrated near the propagating crack front. In contrast, faults and fissures in the subsurface appear to slip or open aseismically coeval with the intrusions. The seismic energy released during dike intrusions in the Manda Hararo Rift appears to be primarily modulated by the local magnitude of differential tensile stress and marginally by the rate of stress change induced by the intrusion. The low level of seismic energy accompanying dike intrusions, despite their significant volumes, is likely an indicator of an overall low level of tension in the lithosphere of this nascent plate boundary.
1525-2027
Q0AB08
Grandin, R.
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Jacques, E.
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Nercessian, A.
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Ayele, A.
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Doubre, C.
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Socquet, A.
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Keir, D.
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Kassim, M.
155b6c21-923d-4476-bd47-a427b1946783
Lemarchand, A.
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King, G.C.P.
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Grandin, R.
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Jacques, E.
4ba743a2-1f4e-45e7-8ab2-6cf791d596f9
Nercessian, A.
c0131455-2b8a-4b09-8516-5883df7949b2
Ayele, A.
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Doubre, C.
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Socquet, A.
8bb92e25-415b-484e-8d91-a6132ec927d1
Keir, D.
5616f81f-bf1b-4678-a167-3160b5647c65
Kassim, M.
155b6c21-923d-4476-bd47-a427b1946783
Lemarchand, A.
1776216c-d8cf-4f31-9e71-efa4d7b30a5e
King, G.C.P.
bffff862-66f5-4950-afc5-f8247bc1b570

Grandin, R., Jacques, E., Nercessian, A., Ayele, A., Doubre, C., Socquet, A., Keir, D., Kassim, M., Lemarchand, A. and King, G.C.P. (2011) Seismicity during lateral dike propagation: Insights from new data in the recent Manda Hararo–Dabbahu rifting episode (Afar, Ethiopia0. Geochemistry, Geophysics, Geosystems, 12, Q0AB08. (doi:10.1029/2010GC003434).

Record type: Article

Abstract

Seismicity released during lateral dike intrusions in the Manda Hararo–Dabbahu Rift (Afar, Ethiopia) provides indirect insight into the distribution and evolution of tensile stress along this magma-assisted divergent plate boundary. In this paper, 5 dike intrusions among the 14 that form the 2005–present rifting episode are analyzed with local and regional seismic data. During dike intrusions, seismicity migrates over distances of 10–15 km at velocities of 0.5–3.0 km/h away from a single reservoir in the center of the rift segment, confirming the analogy with a slow spreading mid-ocean ridge segment. Comparison with geodetic data shows that the reservoir is located 7 km down rift from the topographic summit of the axial depression. Dikes emplaced toward the north are observed to migrate faster and to be more voluminous than those migrating southward, suggesting an asymmetry of tension in the brittle-elastic lithosphere. Seismicity during dike injections is concentrated near the propagating crack front. In contrast, faults and fissures in the subsurface appear to slip or open aseismically coeval with the intrusions. The seismic energy released during dike intrusions in the Manda Hararo Rift appears to be primarily modulated by the local magnitude of differential tensile stress and marginally by the rate of stress change induced by the intrusion. The low level of seismic energy accompanying dike intrusions, despite their significant volumes, is likely an indicator of an overall low level of tension in the lithosphere of this nascent plate boundary.

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Published date: 2011

Identifiers

Local EPrints ID: 187635
URI: http://eprints.soton.ac.uk/id/eprint/187635
ISSN: 1525-2027
PURE UUID: 5fb662eb-967a-48d5-978c-da8fc4c262e0
ORCID for D. Keir: ORCID iD orcid.org/0000-0001-8787-8446

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Date deposited: 17 May 2011 14:13
Last modified: 26 Nov 2021 02:57

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Contributors

Author: R. Grandin
Author: E. Jacques
Author: A. Nercessian
Author: A. Ayele
Author: C. Doubre
Author: A. Socquet
Author: D. Keir ORCID iD
Author: M. Kassim
Author: A. Lemarchand
Author: G.C.P. King

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