Crustal tomographic imaging of a transitional continental rift: the ethiopian rift
In this study we image crustal structure beneath a magmatic continental rift to understand the interplay between crustal stretching and magmatism during the late stages of continental rifting: the Main Ethiopian Rift (MER). The northern sector of this region marks the transition from continental rif...
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Oxford University Press (OUP)
2008
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Online Access: | http://hdl.handle.net/10379/11030 https://doi.org/10.1111/j.1365-246x.2007.03682.x |
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ftnuigalway:oai:aran.library.nuigalway.ie/:10379/11030 2023-06-11T04:13:14+02:00 Crustal tomographic imaging of a transitional continental rift: the ethiopian rift Daly, E. Keir, D. Ebinger, C. J. Stuart, G. W. Bastow, I. D. Ayele, A. 2008-03-01 http://hdl.handle.net/10379/11030 https://doi.org/10.1111/j.1365-246x.2007.03682.x unknown Oxford University Press (OUP) Geophysical Journal International Daly, E. Keir, D.; Ebinger, C. J.; Stuart, G. W.; Bastow, I. D.; Ayele, A. (2008). Crustal tomographic imaging of a transitional continental rift: the ethiopian rift. Geophysical Journal International 172 (3), 1033-1048 0956-540X,1365-246X http://hdl.handle.net/10379/11030 doi:10.1111/j.1365-246x.2007.03682.x Attribution-NonCommercial-NoDerivs 3.0 Ireland https://creativecommons.org/licenses/by-nc-nd/3.0/ie/ tomography earthquake source observations seismic tomography crustal structure africa local earthquake tomography iceland ridge experiment papua-new-guinea velocity structure gravity-data triple junction p-wave simultaneous inversion shallow subduction structure beneath Article 2008 ftnuigalway https://doi.org/10.1111/j.1365-246x.2007.03682.x 2023-05-28T18:05:10Z In this study we image crustal structure beneath a magmatic continental rift to understand the interplay between crustal stretching and magmatism during the late stages of continental rifting: the Main Ethiopian Rift (MER). The northern sector of this region marks the transition from continental rifting in the East African Rift to incipient seafloor spreading in the southern Red Sea and western Gulf of Aden. Our local tomographic inversion exploits 172 broad-band instruments covering an area of 250 x 350 km of the rift and adjacent plateaux. The instruments recorded a total of 2139 local earthquakes over a 16-month period. Several synthetic tests show that resolution is good between 12 and 25 km depth (below sea level), but some horizontal velocity smearing is evident along the axis of the Main Ethiopian Rift below 16 km. We present a 3-D P-wave velocity model of the mid-crust and present the first 3-D Vp/Vs model of the region. Our models show high P-wave velocities (6.5 km s(-1)) beneath the axis of the rift at a depth of 12-25 km. The presence of high Vp/Vs ratios (1.81-1.84) at the same depth range suggest that they are cooled mafic intrusions. The high Vp/Vs values, along with other geophysical evidence, suggest that dyking is pervasive beneath the axis of the rift from the mid-crustal depths to the surface and that some portion of partial melt may exist at lower crustal depths. Although the crustal stretching factor across the Main Ethiopian Rift is similar to 1.7, our results indicate that magma intrusion in narrow zones accommodates a large proportion of extensional strain, with similarities to slow-spreading mid-ocean ridge processes. Article in Journal/Newspaper Iceland National University of Ireland (NUI), Galway: ARAN Geophysical Journal International 172 3 1033 1048 |
institution |
Open Polar |
collection |
National University of Ireland (NUI), Galway: ARAN |
op_collection_id |
ftnuigalway |
language |
unknown |
topic |
tomography earthquake source observations seismic tomography crustal structure africa local earthquake tomography iceland ridge experiment papua-new-guinea velocity structure gravity-data triple junction p-wave simultaneous inversion shallow subduction structure beneath |
spellingShingle |
tomography earthquake source observations seismic tomography crustal structure africa local earthquake tomography iceland ridge experiment papua-new-guinea velocity structure gravity-data triple junction p-wave simultaneous inversion shallow subduction structure beneath Daly, E. Keir, D. Ebinger, C. J. Stuart, G. W. Bastow, I. D. Ayele, A. Crustal tomographic imaging of a transitional continental rift: the ethiopian rift |
topic_facet |
tomography earthquake source observations seismic tomography crustal structure africa local earthquake tomography iceland ridge experiment papua-new-guinea velocity structure gravity-data triple junction p-wave simultaneous inversion shallow subduction structure beneath |
description |
In this study we image crustal structure beneath a magmatic continental rift to understand the interplay between crustal stretching and magmatism during the late stages of continental rifting: the Main Ethiopian Rift (MER). The northern sector of this region marks the transition from continental rifting in the East African Rift to incipient seafloor spreading in the southern Red Sea and western Gulf of Aden. Our local tomographic inversion exploits 172 broad-band instruments covering an area of 250 x 350 km of the rift and adjacent plateaux. The instruments recorded a total of 2139 local earthquakes over a 16-month period. Several synthetic tests show that resolution is good between 12 and 25 km depth (below sea level), but some horizontal velocity smearing is evident along the axis of the Main Ethiopian Rift below 16 km. We present a 3-D P-wave velocity model of the mid-crust and present the first 3-D Vp/Vs model of the region. Our models show high P-wave velocities (6.5 km s(-1)) beneath the axis of the rift at a depth of 12-25 km. The presence of high Vp/Vs ratios (1.81-1.84) at the same depth range suggest that they are cooled mafic intrusions. The high Vp/Vs values, along with other geophysical evidence, suggest that dyking is pervasive beneath the axis of the rift from the mid-crustal depths to the surface and that some portion of partial melt may exist at lower crustal depths. Although the crustal stretching factor across the Main Ethiopian Rift is similar to 1.7, our results indicate that magma intrusion in narrow zones accommodates a large proportion of extensional strain, with similarities to slow-spreading mid-ocean ridge processes. |
format |
Article in Journal/Newspaper |
author |
Daly, E. Keir, D. Ebinger, C. J. Stuart, G. W. Bastow, I. D. Ayele, A. |
author_facet |
Daly, E. Keir, D. Ebinger, C. J. Stuart, G. W. Bastow, I. D. Ayele, A. |
author_sort |
Daly, E. |
title |
Crustal tomographic imaging of a transitional continental rift: the ethiopian rift |
title_short |
Crustal tomographic imaging of a transitional continental rift: the ethiopian rift |
title_full |
Crustal tomographic imaging of a transitional continental rift: the ethiopian rift |
title_fullStr |
Crustal tomographic imaging of a transitional continental rift: the ethiopian rift |
title_full_unstemmed |
Crustal tomographic imaging of a transitional continental rift: the ethiopian rift |
title_sort |
crustal tomographic imaging of a transitional continental rift: the ethiopian rift |
publisher |
Oxford University Press (OUP) |
publishDate |
2008 |
url |
http://hdl.handle.net/10379/11030 https://doi.org/10.1111/j.1365-246x.2007.03682.x |
genre |
Iceland |
genre_facet |
Iceland |
op_relation |
Geophysical Journal International Daly, E. Keir, D.; Ebinger, C. J.; Stuart, G. W.; Bastow, I. D.; Ayele, A. (2008). Crustal tomographic imaging of a transitional continental rift: the ethiopian rift. Geophysical Journal International 172 (3), 1033-1048 0956-540X,1365-246X http://hdl.handle.net/10379/11030 doi:10.1111/j.1365-246x.2007.03682.x |
op_rights |
Attribution-NonCommercial-NoDerivs 3.0 Ireland https://creativecommons.org/licenses/by-nc-nd/3.0/ie/ |
op_doi |
https://doi.org/10.1111/j.1365-246x.2007.03682.x |
container_title |
Geophysical Journal International |
container_volume |
172 |
container_issue |
3 |
container_start_page |
1033 |
op_container_end_page |
1048 |
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1768390014028218368 |