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Seismicity and subsidence following the 2011 Nabro eruption, Eritrea: Insights into the plumbing system of an off-rift volcano

Seismicity and subsidence following the 2011 Nabro eruption, Eritrea: Insights into the plumbing system of an off-rift volcano
Seismicity and subsidence following the 2011 Nabro eruption, Eritrea: Insights into the plumbing system of an off-rift volcano
Nabro volcano, situated to the east of the Afar Rift Zone, erupted on 12 June 2011. Eruptions at such off-rift volcanoes are infrequent, and consequently the plumbing systems are poorly understood. We present post-eruption SAR images from the TerraSAR-X satellite and post-eruption continuous seismic activity from a local seismic array. Interferometric analysis of SAR data, reveals a circular, 12 km wide, signal subsiding at ~200 mm/yr. We inverted for the best fit Mogi source finding a 4 ± 1 × 107 m3/yr volume decrease at 7 ± 1 km depth. Between the 31 August and 7 October 2011, we located 658 and relocated 456 earthquakes with local magnitudes between -0.4 and 4.5. Seismicity beneath the SE edge of Nabro at 11 km depth is likely associated with high strain rates from deep magma flow into the modelled reservoir. This suggests magma is supplied through a narrow conduit and then stored at ~7 ?km depth. We interpret seismicity at 4-6 km depth as brittle fracturing above the inferred magma reservoir. Focal mechanisms delineate a thrust fault striking NE-SW, and dipping 45° to the SE across the caldera floor. We propose the crustal response is to slip on this fault which cross-cuts the caldera, rather than to deform on ring faults. The NE-SW fault plane is not associated with measurable surface deformation, indicating that it does not contribute much to the caldera deformation. We show that subsidence of the caldera is controlled by magma chamber processes, rather than fault slip.
InSAR, microseismicity, focal mechanisms, Afar, geodetic modelling, off-rift volcanism
0148-0227
8267-8282
Hamlyn, J.E.
e0ee72d7-f59f-4cf4-aea7-86c1c0eb440b
Keir, D.
5616f81f-bf1b-4678-a167-3160b5647c65
Wright, T.J.
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Neuberg, J.W
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Goitom, B
a52c5448-ed23-43a1-8dfd-50dfe9355117
Hammond, J.O.S.
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Pagli, C.
f2ee8853-c513-419a-ad33-c457dad669ca
Oppenheimer, C.
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Kendall, J-M.
9a2eb4fe-eb71-4d9b-955b-b56b790c2bf9
Hamlyn, J.E.
e0ee72d7-f59f-4cf4-aea7-86c1c0eb440b
Keir, D.
5616f81f-bf1b-4678-a167-3160b5647c65
Wright, T.J.
aeda4400-2cf2-4875-aade-b1c53f4f4fb7
Neuberg, J.W
2d40a928-fafc-4bfa-ad85-4e0101dc45b1
Goitom, B
a52c5448-ed23-43a1-8dfd-50dfe9355117
Hammond, J.O.S.
df081c77-2e69-4753-8846-549826d905bb
Pagli, C.
f2ee8853-c513-419a-ad33-c457dad669ca
Oppenheimer, C.
2639e0bb-9076-4b00-9015-df912a01ecd6
Kendall, J-M.
9a2eb4fe-eb71-4d9b-955b-b56b790c2bf9

Hamlyn, J.E., Keir, D., Wright, T.J., Neuberg, J.W, Goitom, B, Hammond, J.O.S., Pagli, C., Oppenheimer, C. and Kendall, J-M. (2014) Seismicity and subsidence following the 2011 Nabro eruption, Eritrea: Insights into the plumbing system of an off-rift volcano. Journal of Geophysical Research, 119 (11), 8267-8282. (doi:10.1002/2014JB011395).

Record type: Article

Abstract

Nabro volcano, situated to the east of the Afar Rift Zone, erupted on 12 June 2011. Eruptions at such off-rift volcanoes are infrequent, and consequently the plumbing systems are poorly understood. We present post-eruption SAR images from the TerraSAR-X satellite and post-eruption continuous seismic activity from a local seismic array. Interferometric analysis of SAR data, reveals a circular, 12 km wide, signal subsiding at ~200 mm/yr. We inverted for the best fit Mogi source finding a 4 ± 1 × 107 m3/yr volume decrease at 7 ± 1 km depth. Between the 31 August and 7 October 2011, we located 658 and relocated 456 earthquakes with local magnitudes between -0.4 and 4.5. Seismicity beneath the SE edge of Nabro at 11 km depth is likely associated with high strain rates from deep magma flow into the modelled reservoir. This suggests magma is supplied through a narrow conduit and then stored at ~7 ?km depth. We interpret seismicity at 4-6 km depth as brittle fracturing above the inferred magma reservoir. Focal mechanisms delineate a thrust fault striking NE-SW, and dipping 45° to the SE across the caldera floor. We propose the crustal response is to slip on this fault which cross-cuts the caldera, rather than to deform on ring faults. The NE-SW fault plane is not associated with measurable surface deformation, indicating that it does not contribute much to the caldera deformation. We show that subsidence of the caldera is controlled by magma chamber processes, rather than fault slip.

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Accepted/In Press date: 15 September 2014
Published date: November 2014
Keywords: InSAR, microseismicity, focal mechanisms, Afar, geodetic modelling, off-rift volcanism
Organisations: Geology & Geophysics

Identifiers

Local EPrints ID: 369151
URI: http://eprints.soton.ac.uk/id/eprint/369151
ISSN: 0148-0227
PURE UUID: bf74dc82-578d-4dc1-9a11-bb0483bad078
ORCID for D. Keir: ORCID iD orcid.org/0000-0001-8787-8446

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Date deposited: 22 Sep 2014 13:01
Last modified: 15 Mar 2024 03:38

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Contributors

Author: J.E. Hamlyn
Author: D. Keir ORCID iD
Author: T.J. Wright
Author: J.W Neuberg
Author: B Goitom
Author: J.O.S. Hammond
Author: C. Pagli
Author: C. Oppenheimer
Author: J-M. Kendall

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