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The role of oceanic transform faults in seafloor spreading: a global perspective from seismic anisotropy

The role of oceanic transform faults in seafloor spreading: a global perspective from seismic anisotropy
The role of oceanic transform faults in seafloor spreading: a global perspective from seismic anisotropy
Mantle anisotropy beneath mid-ocean ridges and oceanic transforms is key to our understanding of seafloor spreading and underlying dynamics of divergent plate boundaries. Observations are sparse however, given the remoteness of the oceans and the difficulties of seismic instrumentation. To overcome this we utilise the global distribution of seismicity along transform faults to measure shear wave splitting of over 550 direct S phases recorded at 56 carefully selected seismic stations worldwide. Applying this source-side splitting technique allows for characterisation of the upper mantle seismic anisotropy, and therefore the pattern of mantle flow, directly beneath seismically active transform faults. The majority of the results (60%) return nulls (no splitting), while the non-null measurements display clear azimuthal dependency. This is best simply explained by anisotropy with a near vertical symmetry axis, consistent with mantle upwelling beneath oceanic transforms as suggested by numerical models. It appears therefore that the long-term stability of seafloor spreading may be associated with widespread mantle upwelling beneath the transforms creating warm and weak faults that localise strain to the plate boundary.
2169-9356
1-16
Eakin, Caroline M.
767ea10a-757b-4db5-8705-0c79368f8606
Rychert, Catherine
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Harmon, Nicholas
10d11a16-b8b0-4132-9354-652e72d8e830
Eakin, Caroline M.
767ea10a-757b-4db5-8705-0c79368f8606
Rychert, Catherine
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Harmon, Nicholas
10d11a16-b8b0-4132-9354-652e72d8e830

Eakin, Caroline M., Rychert, Catherine and Harmon, Nicholas (2018) The role of oceanic transform faults in seafloor spreading: a global perspective from seismic anisotropy. Journal of Geophysical Research: Solid Earth, 1-16. (doi:10.1002/2017JB015176).

Record type: Article

Abstract

Mantle anisotropy beneath mid-ocean ridges and oceanic transforms is key to our understanding of seafloor spreading and underlying dynamics of divergent plate boundaries. Observations are sparse however, given the remoteness of the oceans and the difficulties of seismic instrumentation. To overcome this we utilise the global distribution of seismicity along transform faults to measure shear wave splitting of over 550 direct S phases recorded at 56 carefully selected seismic stations worldwide. Applying this source-side splitting technique allows for characterisation of the upper mantle seismic anisotropy, and therefore the pattern of mantle flow, directly beneath seismically active transform faults. The majority of the results (60%) return nulls (no splitting), while the non-null measurements display clear azimuthal dependency. This is best simply explained by anisotropy with a near vertical symmetry axis, consistent with mantle upwelling beneath oceanic transforms as suggested by numerical models. It appears therefore that the long-term stability of seafloor spreading may be associated with widespread mantle upwelling beneath the transforms creating warm and weak faults that localise strain to the plate boundary.

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Accepted/In Press date: 3 February 2018
e-pub ahead of print date: 26 February 2018

Identifiers

Local EPrints ID: 417695
URI: http://eprints.soton.ac.uk/id/eprint/417695
ISSN: 2169-9356
PURE UUID: 4781cca6-4f61-404b-8c09-9507adaade72
ORCID for Nicholas Harmon: ORCID iD orcid.org/0000-0002-0731-768X

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Date deposited: 12 Feb 2018 17:30
Last modified: 07 Oct 2020 01:56

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