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Back-propagating supershear rupture in the 2016 Mw 7.1 Romanche transform fault earthquake

Back-propagating supershear rupture in the 2016 Mw 7.1 Romanche transform fault earthquake
Back-propagating supershear rupture in the 2016 Mw 7.1 Romanche transform fault earthquake
How an earthquake rupture propagates strongly influences the potentially destructive ground shaking. Complex ruptures often involve slip along multiple faults, which masks information on the frictional behaviour of fault zones. Geometrically smooth ocean transform fault plate boundaries offer a favourable environment to study fault dynamics, because strain is accommodated along a single, wide fault zone that offsets the homogeneous geology. Here we present an analysis of the 2016 Mw 7.1 earthquake on the Romanche fracture zone in the equatorial Atlantic, using data from both nearby seafloor seismometers and global seismic networks. We show that this rupture had two phases: (1) upward and eastward propagation towards a weaker region where the transform fault intersects the mid-ocean ridge, and then (2) an unusual back-propagation westwards at a supershear speed towards the centre of the fault. We suggest that deep rupture into weak fault segments facilitated greater seismic slip on shallow locked zones. This highlights that even earthquakes along a single distinct fault zone can be highly dynamic. Observations of back-propagating ruptures are sparse, and the possibility of reverse propagation is largely absent in rupture simulations and unaccounted for in hazard assessments.
1752-0894
647-653
Hicks, Stephen P.
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Okuwaki, Ryo
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Steinberg, Andreas
f84d818b-0a5c-419d-8aa2-62c86978d902
Rychert, Catherine A.
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Harmon, Nicholas
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Abercrombie, Rachel E.
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Bogiatzis, Petros
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Schlaphorst, David
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Zahradnik, Jiri
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Kendall, J-Michael
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Yagi, Yuji
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Shimizu, Kousuke
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Sudhaus, Henriette
c29db415-b21d-420e-8002-aac1db7f5567
Hicks, Stephen P.
036d1b3b-bb7a-4a22-b2ce-71618a1723a3
Okuwaki, Ryo
63c9207a-d983-44b2-a8e3-3b50af20a0d4
Steinberg, Andreas
f84d818b-0a5c-419d-8aa2-62c86978d902
Rychert, Catherine A.
70cf1e3a-58ea-455a-918a-1d570c5e53c5
Harmon, Nicholas
10d11a16-b8b0-4132-9354-652e72d8e830
Abercrombie, Rachel E.
969f3007-9648-4437-8693-21b20eaa6412
Bogiatzis, Petros
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Schlaphorst, David
ce763c91-8236-4eac-b256-b35a8613d62b
Zahradnik, Jiri
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Kendall, J-Michael
0a1d10dd-0a0a-4b02-aefd-cde8741307ce
Yagi, Yuji
7ee122b6-1d9d-4c13-8b3b-e48a7bdf04b9
Shimizu, Kousuke
d226f887-ed09-4afb-b0a8-af464ccc1c54
Sudhaus, Henriette
c29db415-b21d-420e-8002-aac1db7f5567

Hicks, Stephen P., Okuwaki, Ryo, Steinberg, Andreas, Rychert, Catherine A., Harmon, Nicholas, Abercrombie, Rachel E., Bogiatzis, Petros, Schlaphorst, David, Zahradnik, Jiri, Kendall, J-Michael, Yagi, Yuji, Shimizu, Kousuke and Sudhaus, Henriette (2020) Back-propagating supershear rupture in the 2016 Mw 7.1 Romanche transform fault earthquake. Nature Geoscience, 13 (9), 647-653. (doi:10.1038/s41561-020-0619-9).

Record type: Article

Abstract

How an earthquake rupture propagates strongly influences the potentially destructive ground shaking. Complex ruptures often involve slip along multiple faults, which masks information on the frictional behaviour of fault zones. Geometrically smooth ocean transform fault plate boundaries offer a favourable environment to study fault dynamics, because strain is accommodated along a single, wide fault zone that offsets the homogeneous geology. Here we present an analysis of the 2016 Mw 7.1 earthquake on the Romanche fracture zone in the equatorial Atlantic, using data from both nearby seafloor seismometers and global seismic networks. We show that this rupture had two phases: (1) upward and eastward propagation towards a weaker region where the transform fault intersects the mid-ocean ridge, and then (2) an unusual back-propagation westwards at a supershear speed towards the centre of the fault. We suggest that deep rupture into weak fault segments facilitated greater seismic slip on shallow locked zones. This highlights that even earthquakes along a single distinct fault zone can be highly dynamic. Observations of back-propagating ruptures are sparse, and the possibility of reverse propagation is largely absent in rupture simulations and unaccounted for in hazard assessments.

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2016_Romanche_rupture_paper_SHicks_accepted_combined_noembargo_header - Accepted Manuscript
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More information

Accepted/In Press date: 26 June 2020
e-pub ahead of print date: 10 August 2020
Published date: 1 September 2020

Identifiers

Local EPrints ID: 444287
URI: http://eprints.soton.ac.uk/id/eprint/444287
ISSN: 1752-0894
PURE UUID: 0faeb092-a42e-48c7-9798-027f0c4ab4fd
ORCID for Stephen P. Hicks: ORCID iD orcid.org/0000-0002-7476-3284
ORCID for Nicholas Harmon: ORCID iD orcid.org/0000-0002-0731-768X
ORCID for Petros Bogiatzis: ORCID iD orcid.org/0000-0003-1902-7476

Catalogue record

Date deposited: 09 Oct 2020 16:31
Last modified: 26 Nov 2021 05:39

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Contributors

Author: Stephen P. Hicks ORCID iD
Author: Ryo Okuwaki
Author: Andreas Steinberg
Author: Nicholas Harmon ORCID iD
Author: Rachel E. Abercrombie
Author: Petros Bogiatzis ORCID iD
Author: David Schlaphorst
Author: Jiri Zahradnik
Author: J-Michael Kendall
Author: Yuji Yagi
Author: Kousuke Shimizu
Author: Henriette Sudhaus

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