Seismicity and crustal structure of the Southern Main Ethiopian Rift: New evidence from Lake Abaya
Seismicity and crustal structure of the Southern Main Ethiopian Rift: New evidence from Lake Abaya
The Main Ethiopian Rift (MER) has developed during the 18 Ma-Recent separation of the Nubian and Somalian plates. Extension in its central and northern sectors is associated with seismic activity and active magma intrusion, primarily within the rift, where shallow ((Formula presented.) 5 km) seismicity along magmatic centers is commonly caused by fluid flow through open fractures in hydrothermal systems. However, the extent to which similar magmatic rifting persists into the southern MER is unknown. Using data from a temporary network of five seismograph stations, we analyze patterns of seismicity and crustal structure in the Abaya region of the southern MER. Magnitudes range from 0.9 to 4.0; earthquake depths are 0–30 km. (Formula presented.) ratios of (Formula presented.) 1.69, estimated from Wadati diagram analysis, corroborate bulk-crustal (Formula presented.) ratios determined via teleseismic P-to-S receiver function H- (Formula presented.) stacking and reveal a relative lack of mafic intrusion compared to the MER rift sectors to the north. There is a clear association of seismicity with the western border fault system of the MER everywhere in our study area, but earthquake depths are shallow near Duguna volcano, implying a shallowed geothermal gradient associated with rift valley silicic magmatism. This part of the MER is thus interpreted best as a young magmatic system that locally impacts the geothermal gradient but that has not yet significantly modified continental crustal composition via rift-axial magmatic rifting.
East African Rift seismicity, Ethiopia, crustal structure, local seismicity, seismic networks
Ogden, Christopher S.
689ebe48-79de-4fc0-a55d-14b37edd18ba
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Bastow, Ian D.
7a2698d0-d535-4462-a9a9-0e3293d2d667
Ayele, Atalay
730f62fb-c461-4a4e-b52d-b143a7936df6
Marcou, S.
563f55eb-f0d2-4dea-9823-9d792c6ff6a0
Ugo, F.
a21e51a4-60f0-4ce8-9994-f6d88715bf48
Woodward, A.
fbbdccbb-92e6-4659-9fac-ff29975827ee
Kibret, Birhanu A.
353b131c-0ca4-4063-9c62-60a407d0c862
Gudbrandsson, S.
84e78fae-9440-43b3-a752-0ed5655f3d9e
19 July 2021
Ogden, Christopher S.
689ebe48-79de-4fc0-a55d-14b37edd18ba
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Bastow, Ian D.
7a2698d0-d535-4462-a9a9-0e3293d2d667
Ayele, Atalay
730f62fb-c461-4a4e-b52d-b143a7936df6
Marcou, S.
563f55eb-f0d2-4dea-9823-9d792c6ff6a0
Ugo, F.
a21e51a4-60f0-4ce8-9994-f6d88715bf48
Woodward, A.
fbbdccbb-92e6-4659-9fac-ff29975827ee
Kibret, Birhanu A.
353b131c-0ca4-4063-9c62-60a407d0c862
Gudbrandsson, S.
84e78fae-9440-43b3-a752-0ed5655f3d9e
Ogden, Christopher S., Keir, Derek, Bastow, Ian D., Ayele, Atalay, Marcou, S., Ugo, F., Woodward, A., Kibret, Birhanu A. and Gudbrandsson, S.
(2021)
Seismicity and crustal structure of the Southern Main Ethiopian Rift: New evidence from Lake Abaya.
Geochemistry, Geophysics, Geosystems, 22 (8), [e2021GC009831].
(doi:10.1029/2021GC009831).
Abstract
The Main Ethiopian Rift (MER) has developed during the 18 Ma-Recent separation of the Nubian and Somalian plates. Extension in its central and northern sectors is associated with seismic activity and active magma intrusion, primarily within the rift, where shallow ((Formula presented.) 5 km) seismicity along magmatic centers is commonly caused by fluid flow through open fractures in hydrothermal systems. However, the extent to which similar magmatic rifting persists into the southern MER is unknown. Using data from a temporary network of five seismograph stations, we analyze patterns of seismicity and crustal structure in the Abaya region of the southern MER. Magnitudes range from 0.9 to 4.0; earthquake depths are 0–30 km. (Formula presented.) ratios of (Formula presented.) 1.69, estimated from Wadati diagram analysis, corroborate bulk-crustal (Formula presented.) ratios determined via teleseismic P-to-S receiver function H- (Formula presented.) stacking and reveal a relative lack of mafic intrusion compared to the MER rift sectors to the north. There is a clear association of seismicity with the western border fault system of the MER everywhere in our study area, but earthquake depths are shallow near Duguna volcano, implying a shallowed geothermal gradient associated with rift valley silicic magmatism. This part of the MER is thus interpreted best as a young magmatic system that locally impacts the geothermal gradient but that has not yet significantly modified continental crustal composition via rift-axial magmatic rifting.
Text
2021GC009831
- Version of Record
More information
Accepted/In Press date: 29 June 2021
Published date: 19 July 2021
Additional Information:
Funding Information:
The authors thank reviewers Tim Greenfield and Francesco Mazzarini, and editor Maureen Long for their insightful comments. The authors thank SEIS‐UK, supported by the Natural Environment Research Council (NERC) under agreement R8/H10/64, for the loan of all seismic instruments. C. Ogden and I. Bastow acknowledge support from Natural Environment Research Council grant number NE/S014136/1, and Research England GCRF QR Funding. The authors also thank S. Hicks for his advice concerning Non Lin Loc, and T. Merry, R. Kounoudis, and S. Alemayehu for assistance during fieldwork.
Funding Information:
The authors thank reviewers Tim Greenfield and Francesco Mazzarini, and editor Maureen Long for their insightful comments. The authors thank SEIS-UK, supported by the Natural Environment Research Council (NERC) under agreement R8/H10/64, for the loan of all seismic instruments. C. Ogden and I. Bastow acknowledge support from Natural Environment Research Council grant number NE/S014136/1, and Research England GCRF QR Funding. The authors also thank S. Hicks for his advice concerning Non Lin Loc, and T. Merry, R. Kounoudis, and S. Alemayehu for assistance during fieldwork.
Publisher Copyright:
© 2021. The Authors.
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
Keywords:
East African Rift seismicity, Ethiopia, crustal structure, local seismicity, seismic networks
Identifiers
Local EPrints ID: 451294
URI: http://eprints.soton.ac.uk/id/eprint/451294
ISSN: 1525-2027
PURE UUID: 1f3bea22-5d06-4f4f-a0e1-bb89bc23e649
Catalogue record
Date deposited: 17 Sep 2021 16:30
Last modified: 17 Mar 2024 03:24
Export record
Altmetrics
Contributors
Author:
Christopher S. Ogden
Author:
Ian D. Bastow
Author:
Atalay Ayele
Author:
S. Marcou
Author:
F. Ugo
Author:
A. Woodward
Author:
Birhanu A. Kibret
Author:
S. Gudbrandsson
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics
