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Mantle upwelling beneath Madagascar: evidence from receiver function analysis and shear wave splitting

Mantle upwelling beneath Madagascar: evidence from receiver function analysis and shear wave splitting
Mantle upwelling beneath Madagascar: evidence from receiver function analysis and shear wave splitting
Crustal receiver functions have been calculated from 128 events for two three-component broadband seismomenters located on the south coast (FOMA) and in the central High Plateaux (ABPO) of Madagascar. For each station, crustal thickness and Vp/Vs ratio were estimated from H- κ plots. Self-consistent receiver functions from a smaller back-azimuthal range were then selected, stacked and inverted to determine shear wave velocity structure as a function of depth. These results were corroborated by guided forward modeling and by Monte Carlo error analysis. The crust is found to be thinner (39 ± 0.7 km) beneath the highland center of Madagascar compared to the coast (44 ± 1.6 km), which is the opposite of what would be expected for crustal isostasy, suggesting that present-day long wavelength topography is maintained, at least in part, dynamically. This inference of dynamic support is corroborated by shear wave splitting analyses at the same stations, which produce an overwhelming majority of null results (>96 %), as expected for vertical mantle flow or asthenospheric upwelling beneath the island. These findings suggest a sub-plate origin for dynamic support.
1383-4649
825–836
Paul, Jonathan D.
be601f1b-c590-4493-8a28-0b01f2fd719d
Eakin, Caroline M.
767ea10a-757b-4db5-8705-0c79368f8606
Paul, Jonathan D.
be601f1b-c590-4493-8a28-0b01f2fd719d
Eakin, Caroline M.
767ea10a-757b-4db5-8705-0c79368f8606

Paul, Jonathan D. and Eakin, Caroline M. (2017) Mantle upwelling beneath Madagascar: evidence from receiver function analysis and shear wave splitting. Journal of Seismology, 21 (4), 825–836. (doi:10.1007/s10950-016-9637-x).

Record type: Article

Abstract

Crustal receiver functions have been calculated from 128 events for two three-component broadband seismomenters located on the south coast (FOMA) and in the central High Plateaux (ABPO) of Madagascar. For each station, crustal thickness and Vp/Vs ratio were estimated from H- κ plots. Self-consistent receiver functions from a smaller back-azimuthal range were then selected, stacked and inverted to determine shear wave velocity structure as a function of depth. These results were corroborated by guided forward modeling and by Monte Carlo error analysis. The crust is found to be thinner (39 ± 0.7 km) beneath the highland center of Madagascar compared to the coast (44 ± 1.6 km), which is the opposite of what would be expected for crustal isostasy, suggesting that present-day long wavelength topography is maintained, at least in part, dynamically. This inference of dynamic support is corroborated by shear wave splitting analyses at the same stations, which produce an overwhelming majority of null results (>96 %), as expected for vertical mantle flow or asthenospheric upwelling beneath the island. These findings suggest a sub-plate origin for dynamic support.

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More information

Accepted/In Press date: 21 December 2016
e-pub ahead of print date: 9 January 2017
Published date: 1 July 2017
Organisations: Geology & Geophysics

Identifiers

Local EPrints ID: 406528
URI: http://eprints.soton.ac.uk/id/eprint/406528
ISSN: 1383-4649
PURE UUID: 005edea8-c82c-4e8c-86d2-1eb77a8eac10

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Date deposited: 18 Mar 2017 02:22
Last modified: 08 Jan 2022 01:19

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Contributors

Author: Jonathan D. Paul
Author: Caroline M. Eakin

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