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Upper crustal structure of an active volcano from refraction/reflection tomography, Montserrat, Lesser Antilles

Upper crustal structure of an active volcano from refraction/reflection tomography, Montserrat, Lesser Antilles
Upper crustal structure of an active volcano from refraction/reflection tomography, Montserrat, Lesser Antilles
To better understand the volcanic phenomena acting on Montserrat, the SEA-CALIPSO seis-mic experiment (Seismic Experiment with Airgun-source – Caribbean Andesitic Lava Island Precision Seismo-geodetic Observatory) was conducted in 2007 December with the aim of imaging the upper crust and the magmatic system feeding the active Soufri ?ere Hills Volcano. The 3-D survey covered an area of about 50 × 40 km and involved the deployment of 247 land stations and ocean-bottom seismometers (OBSs). A subset of the data, recorded by four OBSs and four land stations on a southeast to northwest line, has been analysed, and traveltimes have been inverted to obtain a 2-D seismic velocity model through the island. Inverted phases include crustal and sediment P waves and wide-angle reflections. The resulting velocity model reveals the presence of a high velocity body (3.5–5.5 km s?1 ) beneath the island, with highest velocities beneath the Soufri ?ere and Centre Hills, cor responding primarily to the cores of these volcanic edifices, built of a pile of andesite lava domes and subsequent intrusions. In the off-shore region, velocities in the surficial sediment layer vary from 1.5 to 3.0 km s?1 , consistent with a mainly calcareous and volcaniclastic composition. A wide-angle reflector is observed at a depth of ?1200 m below the seabed, and appears to deepen beneath the island. The upper crust beneath this reflector has velocities of 4.0–6.0 km s?1 and is infer red to cor respond to plutonic and hypabyssal rocks and sedimentary material of the old arc. The high velocity region beneath the island, extends into the crust to a depth of at least 5 km, and is believed to be caused by an intrusive complex, possibly of intermediate composition. A low velocity zone, as would be expected in the presence of an active magma chamber, was not observed perhaps due to the limited resolution beneath ?5 km depth. Our results so far provide the first wide-angle seismic constraints on the upper crustal structure of the island to a depth of 10 km, and will help understanding the processes that drive volcanism at Montserrat and other island arc volcanoes.
controlled source seismology, seismic tomography, volcano seismology, volcanic arc processes, crustal structure, volcano monitoring
0956-540X
685-696
Paulatto, M.
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Minshull, T.A.
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Baptie, B.
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Dean, S.
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Hammond, J.O.S.
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Henstock, T.
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Kenedi, C.L.
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Kiddle, E.J.
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Malin, P.
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Peirce, C.
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Ryan, G.
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Shalev, E.
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Sparks, R.S.J.
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Voight, B.
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Paulatto, M.
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Minshull, T.A.
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Baptie, B.
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Dean, S.
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Hammond, J.O.S.
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Henstock, T.
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Kenedi, C.L.
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Kiddle, E.J.
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Malin, P.
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Peirce, C.
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Ryan, G.
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Shalev, E.
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Sparks, R.S.J.
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Voight, B.
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Paulatto, M., Minshull, T.A., Baptie, B., Dean, S., Hammond, J.O.S., Henstock, T., Kenedi, C.L., Kiddle, E.J., Malin, P., Peirce, C., Ryan, G., Shalev, E., Sparks, R.S.J. and Voight, B. (2010) Upper crustal structure of an active volcano from refraction/reflection tomography, Montserrat, Lesser Antilles. Geophysical Journal International, 180 (2), 685-696. (doi:10.1111/j.1365-246X.2009.04445.x).

Record type: Article

Abstract

To better understand the volcanic phenomena acting on Montserrat, the SEA-CALIPSO seis-mic experiment (Seismic Experiment with Airgun-source – Caribbean Andesitic Lava Island Precision Seismo-geodetic Observatory) was conducted in 2007 December with the aim of imaging the upper crust and the magmatic system feeding the active Soufri ?ere Hills Volcano. The 3-D survey covered an area of about 50 × 40 km and involved the deployment of 247 land stations and ocean-bottom seismometers (OBSs). A subset of the data, recorded by four OBSs and four land stations on a southeast to northwest line, has been analysed, and traveltimes have been inverted to obtain a 2-D seismic velocity model through the island. Inverted phases include crustal and sediment P waves and wide-angle reflections. The resulting velocity model reveals the presence of a high velocity body (3.5–5.5 km s?1 ) beneath the island, with highest velocities beneath the Soufri ?ere and Centre Hills, cor responding primarily to the cores of these volcanic edifices, built of a pile of andesite lava domes and subsequent intrusions. In the off-shore region, velocities in the surficial sediment layer vary from 1.5 to 3.0 km s?1 , consistent with a mainly calcareous and volcaniclastic composition. A wide-angle reflector is observed at a depth of ?1200 m below the seabed, and appears to deepen beneath the island. The upper crust beneath this reflector has velocities of 4.0–6.0 km s?1 and is infer red to cor respond to plutonic and hypabyssal rocks and sedimentary material of the old arc. The high velocity region beneath the island, extends into the crust to a depth of at least 5 km, and is believed to be caused by an intrusive complex, possibly of intermediate composition. A low velocity zone, as would be expected in the presence of an active magma chamber, was not observed perhaps due to the limited resolution beneath ?5 km depth. Our results so far provide the first wide-angle seismic constraints on the upper crustal structure of the island to a depth of 10 km, and will help understanding the processes that drive volcanism at Montserrat and other island arc volcanoes.

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Submitted date: 6 May 2009
Published date: 1 February 2010
Keywords: controlled source seismology, seismic tomography, volcano seismology, volcanic arc processes, crustal structure, volcano monitoring
Organisations: Ocean and Earth Science

Identifiers

Local EPrints ID: 72172
URI: http://eprints.soton.ac.uk/id/eprint/72172
ISSN: 0956-540X
PURE UUID: bc457ea9-accb-4e47-863a-39699c30bc84
ORCID for T.A. Minshull: ORCID iD orcid.org/0000-0002-8202-1379
ORCID for T. Henstock: ORCID iD orcid.org/0000-0002-2132-2514

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Date deposited: 27 Jan 2010
Last modified: 14 Mar 2024 02:44

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Contributors

Author: M. Paulatto
Author: T.A. Minshull ORCID iD
Author: B. Baptie
Author: S. Dean
Author: J.O.S. Hammond
Author: T. Henstock ORCID iD
Author: C.L. Kenedi
Author: E.J. Kiddle
Author: P. Malin
Author: C. Peirce
Author: G. Ryan
Author: E. Shalev
Author: R.S.J. Sparks
Author: B. Voight

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