Imperial College London
Alternate

Dr Ian Bastow

Faculty of Engineering, Department of Earth Science & Engineering

Senior Lecturer
 
 
 
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Contact

 

+44 (0)20 7594 2974i.bastow Website

 
 
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Location

 

4.45Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Bastow:2015:10.1002/2015JB012228,
author = {Bastow, ID and Darbyshire, FA and Forte, AM and HIbbs, TE and Calvel, A and Gonzalez-Monteza, A and Schow, B},
doi = {10.1002/2015JB012228},
journal = {Journal of Geophysical Research. Solid Earth},
pages = {8404--8421},
title = {Variability and origin of seismic anisotropy across eastern Canada: evidence from shear-wave splitting measurements},
url = {http://dx.doi.org/10.1002/2015JB012228},
volume = {120},
year = {2015}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - Measurements of seismic anisotropy in continental regions are frequently interpreted with respect to past tectonic processes, preserved in the lithosphere as “fossil” fabrics. Models of the present-day sublithospheric flow (often using absolute plate motion as a proxy) are also used to explain the observations. Discriminating between these different sources of seismic anisotropy is particularly challenging beneath shields, whose thick (≥200 km) lithospheric roots may record a protracted history of deformation and strongly influence underlying mantle flow. Eastern Canada, where the geological record spans ∼3 Ga of Earth history, is an ideal region to address this issue. We use shear wave splitting measurements of core phases such as SKS to define upper mantle anisotropy using the orientation of the fast-polarization direction  and delay time δt between fast and slow shear wave arrivals. Comparison with structural trends in surface geology and aeromagnetic data helps to determine the contribution of fossil lithospheric fabrics to the anisotropy. We also assess the influence of sublithospheric mantle flow via flow directions derived from global geodynamic models. Fast-polarization orientations are generally ENE-WSW to ESE-WNW across the region, but significant lateral variability in splitting parameters on a ≤100 km scale implies a lithospheric contribution to the results. Correlations with structural geologic and magnetic trends are not ubiquitous, however, nor are correlations with geodynamically predicted mantle flow directions. We therefore consider that the splitting parameters likely record a combination of the present-day mantle flow and older lithospheric fabrics. Consideration of both sources of anisotropy is critical in shield regions when interpreting splitting observations.
AU  - Bastow,ID
AU  - Darbyshire,FA
AU  - Forte,AM
AU  - HIbbs,TE
AU  - Calvel,A
AU  - Gonzalez-Monteza,A
AU  - Schow,B
DO  - 10.1002/2015JB012228
EP  - 8421
PY  - 2015///
SN  - 2169-9313
SP  - 8404
TI  - Variability and origin of seismic anisotropy across eastern Canada: evidence from shear-wave splitting measurements
T2  - Journal of Geophysical Research. Solid Earth
UR  - http://dx.doi.org/10.1002/2015JB012228
UR  - http://hdl.handle.net/10044/1/27650
VL  - 120
ER  -
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