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Extension and stress during continental breakup: Seismic anisotropy of the crust in Northern Afar

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Extension and stress during continental breakup : Seismic anisotropy of the crust in Northern Afar. / Illsley-Kemp, Finnigan; Savage, Martha K.; Keir, Derek; Hirschberg, Hamish P.; Bull, Jonathan M.; Gernon, Thomas M.; Hammond, James O.S.; Kendall, J.-Michael; Ayele, Atalay; Goitom, Berhe.

In: Earth and Planetary Science Letters, Vol. 477, 01.11.2017, p. 41-51.

Research output: Contribution to journalArticle

Harvard

Illsley-Kemp, F, Savage, MK, Keir, D, Hirschberg, HP, Bull, JM, Gernon, TM, Hammond, JOS, Kendall, J-M, Ayele, A & Goitom, B 2017, 'Extension and stress during continental breakup: Seismic anisotropy of the crust in Northern Afar', Earth and Planetary Science Letters, vol. 477, pp. 41-51. https://doi.org/10.1016/j.epsl.2017.08.014

APA

Illsley-Kemp, F., Savage, M. K., Keir, D., Hirschberg, H. P., Bull, J. M., Gernon, T. M., ... Goitom, B. (2017). Extension and stress during continental breakup: Seismic anisotropy of the crust in Northern Afar. Earth and Planetary Science Letters, 477, 41-51. https://doi.org/10.1016/j.epsl.2017.08.014

Vancouver

Illsley-Kemp F, Savage MK, Keir D, Hirschberg HP, Bull JM, Gernon TM et al. Extension and stress during continental breakup: Seismic anisotropy of the crust in Northern Afar. Earth and Planetary Science Letters. 2017 Nov 1;477:41-51. https://doi.org/10.1016/j.epsl.2017.08.014

Author

Illsley-Kemp, Finnigan ; Savage, Martha K. ; Keir, Derek ; Hirschberg, Hamish P. ; Bull, Jonathan M. ; Gernon, Thomas M. ; Hammond, James O.S. ; Kendall, J.-Michael ; Ayele, Atalay ; Goitom, Berhe. / Extension and stress during continental breakup : Seismic anisotropy of the crust in Northern Afar. In: Earth and Planetary Science Letters. 2017 ; Vol. 477. pp. 41-51.

Bibtex

@article{831ab244d7ba457cb186ffbd361d1732,
title = "Extension and stress during continental breakup: Seismic anisotropy of the crust in Northern Afar",
abstract = "Studies that attempt to simulate continental rifting and subsequent breakup require detailed knowledge of crustal stresses, however observational constraints from continental rifts are lacking. In addition, a knowledge of the stress field around active volcanoes can be used to detect sub-surface changes to the volcanic system. Here we use shear wave splitting to measure the seismic anisotropy of the crust in Northern Afar, a region of active, magma-rich continental breakup. We combine shear wave splitting tomography with modelling of gravitational and magmatic induced stresses to propose a model for crustal stress and strain across the rift. Results show that at the Ethiopian Plateau, seismic anisotropy is consistently oriented N–S. Seismic anisotropy within the rift is generally oriented NNW–SSE, with the exception of regions north and south of the Danakil Depression where seismic anisotropy is rift-perpendicular. These results suggest that the crust at the rift axis is characterized by rift-aligned structures and melt inclusions, consistent with a focusing of tectonic extension at the rift axis. In contrast, we show that at regions within the rift where extension rate is minimal the seismic anisotropy is best explained by the gravitationally induced stress field originating from variations in crustal thickness. Seismic anisotropy away from the rift is controlled by a combination of inherited crustal structures and gravitationally induced extension whereas at the Dabbahu region we show that the stress field changes orientation in response to magmatic intrusions. Our proposed model provides a benchmark of crustal stress in Northern Afar which will aid the monitoring of volcanic hazard. In addition we show that gravitational forces play a key role in measurements of seismic anisotropy, and must be considered in future studies. We demonstrate that during the final stages of continental rifting the stress field at the rift axis is primarily controlled by tectonic extension, but that gravitational forces and magmatic intrusions can play a key role in the orientation of the stress field.",
keywords = "Afar, seismic anisotropy, continental rifting, crustal stress",
author = "Finnigan Illsley-Kemp and Savage, {Martha K.} and Derek Keir and Hirschberg, {Hamish P.} and Bull, {Jonathan M.} and Gernon, {Thomas M.} and Hammond, {James O.S.} and J.-Michael Kendall and Atalay Ayele and Berhe Goitom",
year = "2017",
month = "11",
day = "1",
doi = "10.1016/j.epsl.2017.08.014",
language = "English",
volume = "477",
pages = "41--51",
journal = "Earth and Planetary Science Letters",
issn = "0012-821X",
publisher = "North-Holland Publishing Company",

}

RIS - suitable for import to EndNote

TY - JOUR

T1 - Extension and stress during continental breakup

T2 - Seismic anisotropy of the crust in Northern Afar

AU - Illsley-Kemp, Finnigan

AU - Savage, Martha K.

AU - Keir, Derek

AU - Hirschberg, Hamish P.

AU - Bull, Jonathan M.

AU - Gernon, Thomas M.

AU - Hammond, James O.S.

AU - Kendall, J.-Michael

AU - Ayele, Atalay

AU - Goitom, Berhe

PY - 2017/11/1

Y1 - 2017/11/1

N2 - Studies that attempt to simulate continental rifting and subsequent breakup require detailed knowledge of crustal stresses, however observational constraints from continental rifts are lacking. In addition, a knowledge of the stress field around active volcanoes can be used to detect sub-surface changes to the volcanic system. Here we use shear wave splitting to measure the seismic anisotropy of the crust in Northern Afar, a region of active, magma-rich continental breakup. We combine shear wave splitting tomography with modelling of gravitational and magmatic induced stresses to propose a model for crustal stress and strain across the rift. Results show that at the Ethiopian Plateau, seismic anisotropy is consistently oriented N–S. Seismic anisotropy within the rift is generally oriented NNW–SSE, with the exception of regions north and south of the Danakil Depression where seismic anisotropy is rift-perpendicular. These results suggest that the crust at the rift axis is characterized by rift-aligned structures and melt inclusions, consistent with a focusing of tectonic extension at the rift axis. In contrast, we show that at regions within the rift where extension rate is minimal the seismic anisotropy is best explained by the gravitationally induced stress field originating from variations in crustal thickness. Seismic anisotropy away from the rift is controlled by a combination of inherited crustal structures and gravitationally induced extension whereas at the Dabbahu region we show that the stress field changes orientation in response to magmatic intrusions. Our proposed model provides a benchmark of crustal stress in Northern Afar which will aid the monitoring of volcanic hazard. In addition we show that gravitational forces play a key role in measurements of seismic anisotropy, and must be considered in future studies. We demonstrate that during the final stages of continental rifting the stress field at the rift axis is primarily controlled by tectonic extension, but that gravitational forces and magmatic intrusions can play a key role in the orientation of the stress field.

AB - Studies that attempt to simulate continental rifting and subsequent breakup require detailed knowledge of crustal stresses, however observational constraints from continental rifts are lacking. In addition, a knowledge of the stress field around active volcanoes can be used to detect sub-surface changes to the volcanic system. Here we use shear wave splitting to measure the seismic anisotropy of the crust in Northern Afar, a region of active, magma-rich continental breakup. We combine shear wave splitting tomography with modelling of gravitational and magmatic induced stresses to propose a model for crustal stress and strain across the rift. Results show that at the Ethiopian Plateau, seismic anisotropy is consistently oriented N–S. Seismic anisotropy within the rift is generally oriented NNW–SSE, with the exception of regions north and south of the Danakil Depression where seismic anisotropy is rift-perpendicular. These results suggest that the crust at the rift axis is characterized by rift-aligned structures and melt inclusions, consistent with a focusing of tectonic extension at the rift axis. In contrast, we show that at regions within the rift where extension rate is minimal the seismic anisotropy is best explained by the gravitationally induced stress field originating from variations in crustal thickness. Seismic anisotropy away from the rift is controlled by a combination of inherited crustal structures and gravitationally induced extension whereas at the Dabbahu region we show that the stress field changes orientation in response to magmatic intrusions. Our proposed model provides a benchmark of crustal stress in Northern Afar which will aid the monitoring of volcanic hazard. In addition we show that gravitational forces play a key role in measurements of seismic anisotropy, and must be considered in future studies. We demonstrate that during the final stages of continental rifting the stress field at the rift axis is primarily controlled by tectonic extension, but that gravitational forces and magmatic intrusions can play a key role in the orientation of the stress field.

KW - Afar

KW - seismic anisotropy

KW - continental rifting

KW - crustal stress

U2 - 10.1016/j.epsl.2017.08.014

DO - 10.1016/j.epsl.2017.08.014

M3 - Article

VL - 477

SP - 41

EP - 51

JO - Earth and Planetary Science Letters

JF - Earth and Planetary Science Letters

SN - 0012-821X

ER -