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What causes subsidence following the 2011 eruption at Nabro (Eritrea)?

What causes subsidence following the 2011 eruption at Nabro (Eritrea)?
What causes subsidence following the 2011 eruption at Nabro (Eritrea)?
A major goal in volcanology is to be able to constrain the physical properties of a volcanic system using surface observations. The behaviour of a volcanic system following an eruption can provide powerful constraints on these properties and can provide valuable information for understanding future hazard. We use spatially and temporally dense observations of surface deformation following the 12 June 2011 eruption of Nabro (Eritrea) to place constraints on the mechanics of its subsurface volcanic system. Nabro was imaged 129 times by TerraSAR-X and COSMO-SkyMed satellites during a 15-month period following the eruption. We have produced a detailed time series of the line-of-sight (LOS) displacements at Nabro, finding that the volcano subsides during the entire observation period at a decaying rate. We found significant atmospheric artefacts remained in the data set after a standard spatio-temporal filter was applied. Applying an empirical correction using a linear phase-elevation relationship removed artefacts but also removed real topographically correlated deformation. Instead, we were able to correct each SAR acquisition using independent delay estimates derived from the ECMWF ERA-Interim (ERA-I) global atmospheric model. The corrected time series can be modelled with the deflation of a Mogi source at ∼ 6.4 ± 0.3 km depth. Modelling the time series using viscoelastic relaxation of a shell which surrounds a spherical magma chamber can explain the observed subsidence without a source of further volume loss if the magma is compressible. CO2 outgassing is also a possible cause of continued subsidence. Contraction due to cooling and crystallisation, however, is probably minor. If any post-eruptive recharge of the magmatic system at Nabro is occurring, the rate of recharge must be slower than the post-eruptive relaxation processes. Combined with the lack of pre-eruptive inflation, we suggest that recharge of the magmatic system at Nabro either occurs at a rate that is slower than our detection limit, or it occurs episodically. This case study demonstrates the power of long, dense geodetic time series at volcanoes.
2197-4284
Hamlyn, Joanna
43b2a6da-ee18-4203-9172-ce0accef5189
Wright, Tim
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Walters, Richard
0227212f-8025-4a9e-b4ec-d22a61253909
Sansosti, Eugenio
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Casu, Francesco
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Pepe, Susi
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Edmonds, Marie
1a15ec2e-35cb-4dc1-92b4-f29b7f5d1cc2
McCormick Kilbride, Brendan
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Keir, Derek
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Neuberg, Jurgen
186407d2-9594-49d5-9549-985a4e40e5d8
Oppenheimer, Clive
5f7a0a02-1306-4f6a-bd5f-9c4cdb0ccc21
Hamlyn, Joanna
43b2a6da-ee18-4203-9172-ce0accef5189
Wright, Tim
4ca66524-97a5-4684-80a7-5ab6c908117d
Walters, Richard
0227212f-8025-4a9e-b4ec-d22a61253909
Sansosti, Eugenio
6c01ee45-9b4c-466b-bfaf-fbe2ec3a2251
Casu, Francesco
63b9dd85-b601-4267-bf96-a60b63bfa66e
Pepe, Susi
f9f47729-ffd2-4759-9a13-8ac169084dce
Edmonds, Marie
1a15ec2e-35cb-4dc1-92b4-f29b7f5d1cc2
McCormick Kilbride, Brendan
5db43b4c-2794-4f01-abd4-894b282b2f95
Keir, Derek
5616f81f-bf1b-4678-a167-3160b5647c65
Neuberg, Jurgen
186407d2-9594-49d5-9549-985a4e40e5d8
Oppenheimer, Clive
5f7a0a02-1306-4f6a-bd5f-9c4cdb0ccc21

Hamlyn, Joanna, Wright, Tim, Walters, Richard, Sansosti, Eugenio, Casu, Francesco, Pepe, Susi, Edmonds, Marie, McCormick Kilbride, Brendan, Keir, Derek, Neuberg, Jurgen and Oppenheimer, Clive (2018) What causes subsidence following the 2011 eruption at Nabro (Eritrea)? Progress in Earth and Planetary Science, 5 (31). (doi:10.1186/s40645-018-0186-5).

Record type: Article

Abstract

A major goal in volcanology is to be able to constrain the physical properties of a volcanic system using surface observations. The behaviour of a volcanic system following an eruption can provide powerful constraints on these properties and can provide valuable information for understanding future hazard. We use spatially and temporally dense observations of surface deformation following the 12 June 2011 eruption of Nabro (Eritrea) to place constraints on the mechanics of its subsurface volcanic system. Nabro was imaged 129 times by TerraSAR-X and COSMO-SkyMed satellites during a 15-month period following the eruption. We have produced a detailed time series of the line-of-sight (LOS) displacements at Nabro, finding that the volcano subsides during the entire observation period at a decaying rate. We found significant atmospheric artefacts remained in the data set after a standard spatio-temporal filter was applied. Applying an empirical correction using a linear phase-elevation relationship removed artefacts but also removed real topographically correlated deformation. Instead, we were able to correct each SAR acquisition using independent delay estimates derived from the ECMWF ERA-Interim (ERA-I) global atmospheric model. The corrected time series can be modelled with the deflation of a Mogi source at ∼ 6.4 ± 0.3 km depth. Modelling the time series using viscoelastic relaxation of a shell which surrounds a spherical magma chamber can explain the observed subsidence without a source of further volume loss if the magma is compressible. CO2 outgassing is also a possible cause of continued subsidence. Contraction due to cooling and crystallisation, however, is probably minor. If any post-eruptive recharge of the magmatic system at Nabro is occurring, the rate of recharge must be slower than the post-eruptive relaxation processes. Combined with the lack of pre-eruptive inflation, we suggest that recharge of the magmatic system at Nabro either occurs at a rate that is slower than our detection limit, or it occurs episodically. This case study demonstrates the power of long, dense geodetic time series at volcanoes.

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Accepted/In Press date: 25 April 2018
e-pub ahead of print date: 7 June 2018
Published date: 7 June 2018

Identifiers

Local EPrints ID: 421853
URI: http://eprints.soton.ac.uk/id/eprint/421853
ISSN: 2197-4284
PURE UUID: 1f08683a-bac1-455d-ad9f-c5cc289521cb
ORCID for Derek Keir: ORCID iD orcid.org/0000-0001-8787-8446

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Date deposited: 02 Jul 2018 16:30
Last modified: 10 Jan 2022 02:57

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Contributors

Author: Joanna Hamlyn
Author: Tim Wright
Author: Richard Walters
Author: Eugenio Sansosti
Author: Francesco Casu
Author: Susi Pepe
Author: Marie Edmonds
Author: Brendan McCormick Kilbride
Author: Derek Keir ORCID iD
Author: Jurgen Neuberg
Author: Clive Oppenheimer

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