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Seismic slip on an upper-plate normal fault during a large subduction megathrust rupture

Seismic slip on an upper-plate normal fault during a large subduction megathrust rupture
Seismic slip on an upper-plate normal fault during a large subduction megathrust rupture
Quantification of stress accumulation and release during subduction zone seismic cycles requires an understanding of the distribution of fault slip during earthquakes. Reconstructions of slip are typically constrained to a single, known fault plane. Yet, slip has been shown to occur on multiple faults within the subducting plate1 owing to stress triggering2, resulting in phenomena such as earthquake doublets3. However, rapid stress triggering from the plate interface to faults in the overriding plate has not been documented. Here we analyse seismic data from the magnitude 7.1 Araucania earthquake that occurred in the Chilean subduction zone in 2011. We find that the earthquake, which was reported as a single event in global moment tensor solutions4, 5, was instead composed of two ruptures on two separate faults. Within 12?s a thrust earthquake on the plate interface triggered a second large rupture on a normal fault 30?km away in the overriding plate. This configuration of partitioned rupture is consistent with normal-faulting mechanisms in the ensuing aftershock sequence. We conclude that plate interface rupture can trigger almost instantaneous slip in the overriding plate of a subduction zone. This shallow upper-plate rupture may be masked from teleseismic data, posing a challenge for real-time tsunami warning systems.
1752-0894
955-960
Hicks, Stephen P.
036d1b3b-bb7a-4a22-b2ce-71618a1723a3
Rietbrock, Andreas
e4656f22-06be-40fe-8f98-7f88c351c434
Hicks, Stephen P.
036d1b3b-bb7a-4a22-b2ce-71618a1723a3
Rietbrock, Andreas
e4656f22-06be-40fe-8f98-7f88c351c434

Hicks, Stephen P. and Rietbrock, Andreas (2015) Seismic slip on an upper-plate normal fault during a large subduction megathrust rupture. Nature Geoscience, 8 (12), 955-960. (doi:10.1038/ngeo2585).

Record type: Article

Abstract

Quantification of stress accumulation and release during subduction zone seismic cycles requires an understanding of the distribution of fault slip during earthquakes. Reconstructions of slip are typically constrained to a single, known fault plane. Yet, slip has been shown to occur on multiple faults within the subducting plate1 owing to stress triggering2, resulting in phenomena such as earthquake doublets3. However, rapid stress triggering from the plate interface to faults in the overriding plate has not been documented. Here we analyse seismic data from the magnitude 7.1 Araucania earthquake that occurred in the Chilean subduction zone in 2011. We find that the earthquake, which was reported as a single event in global moment tensor solutions4, 5, was instead composed of two ruptures on two separate faults. Within 12?s a thrust earthquake on the plate interface triggered a second large rupture on a normal fault 30?km away in the overriding plate. This configuration of partitioned rupture is consistent with normal-faulting mechanisms in the ensuing aftershock sequence. We conclude that plate interface rupture can trigger almost instantaneous slip in the overriding plate of a subduction zone. This shallow upper-plate rupture may be masked from teleseismic data, posing a challenge for real-time tsunami warning systems.

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Accepted/In Press date: 13 October 2015
Published date: 1 December 2015
Organisations: Ocean and Earth Science, Geology & Geophysics

Identifiers

Local EPrints ID: 405573
URI: http://eprints.soton.ac.uk/id/eprint/405573
ISSN: 1752-0894
PURE UUID: 39c17a3f-1b6e-4b19-8e3a-3154ca521974
ORCID for Stephen P. Hicks: ORCID iD orcid.org/0000-0002-7476-3284

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Date deposited: 06 Feb 2017 14:19
Last modified: 08 Jan 2022 12:45

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Contributors

Author: Stephen P. Hicks ORCID iD
Author: Andreas Rietbrock

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