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Three-dimensional crustal structure of Ascension Island from active source seismic tomography

Evangelidis, C., Minshull, T.A. and Henstock, T.J. (2004) Three-dimensional crustal structure of Ascension Island from active source seismic tomography Geophysical Journal International, 159, (1), pp. 311-325. (doi:10.1111/j.1365-246X.2004.02396.x).

Record type: Article

Abstract

We present a crustal velocity and Moho depth model of the Ascension volcanic edifice using one of the most densely sampled 3-D wide-angle data sets for volcanic islands currently available. We invert traveltimes of first and second arrivals by seeking a layer-interface minimum structure model, and then test the resulting velocity model by gravity modelling and a 3-D checkerboard resolution test. Within the shallow extrusive part of the crust, two main high-velocity regions coincide with the highest topography on land and the gravity maximum off the west coast of the island, respectively. These features are connected with a high-velocity intrusive core that is created either within or on the top of oceanic layer 3 and is interpreted as a possible relic magma chamber. The thickness of the surface low-velocity region is similar to that observed at Hawaii, Jasper seamount and Great Meteor seamount, suggesting a similar process of edifice construction. The mean density of the volcanic edifice is significantly less than that of normal oceanic crust and than load densities typically assumed in studies of flexure as a result of seamount loading. There is no simple flexural model that explains the shape of the Moho beneath the island, perhaps because of the long-lived volcanism and the proximity of the island to the Mid-Atlantic Ridge (MAR) and the Ascension fracture zone. There is no evidence for magmatic underplating beneath Ascension Island.

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Published date: 2004
Keywords: 3D checkerboard, flexure, high-velocity anomaly, seismic tomography, south atlantic ocean, volcanic islands

Identifiers

Local EPrints ID: 12670
URI: http://eprints.soton.ac.uk/id/eprint/12670
ISSN: 0956-540X
PURE UUID: 96d77947-2b2b-465e-9961-1ffd19e8bba7
ORCID for T.A. Minshull: ORCID iD orcid.org/0000-0002-8202-1379
ORCID for T.J. Henstock: ORCID iD orcid.org/0000-0002-2132-2514

Catalogue record

Date deposited: 02 Dec 2004
Last modified: 17 Jul 2017 17:02

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Contributors

Author: C. Evangelidis
Author: T.A. Minshull ORCID iD
Author: T.J. Henstock ORCID iD

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