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Seismic properties and processes along the subduction plate interface: the February 2010 Mw 8.8 Maule, Chile earthquake

Seismic properties and processes along the subduction plate interface: the February 2010 Mw 8.8 Maule, Chile earthquake
Seismic properties and processes along the subduction plate interface: the February 2010 Mw 8.8 Maule, Chile earthquake
The seismogenic zone of subduction margins has the potential to generate some of the world’s largest earthquakes. A detailed study of the 2010 Mw 8.8 Maule, Chile rupture has enabled interpretation of the controls that govern subduction zone seismic behaviour across the earthquake cycle. In this thesis, we focus on two aspects of the central Chile margin: (1) imaging physical properties in the forearc and along the plate interface; (2) assessing source complexity of megathrust ruptures.

We exploit a dataset of seismic body wave onset times from local aftershocks recorded on a temporary network to derive a 3-D seismic velocity model of the Maule rupture area. We image the main domains of the subduction zone and find a high velocity anomaly located along the plate interface, which we initially interpret as a subducted topographic high. We then develop a second, more accurate velocity model that uses an improved arrival time dataset together with observations from ocean-bottom seismometers. This refined model gives a sharper view of both the plate interface close to the trench, and the marine forearc. We show that ancient blocks of dense mantle in the lower forearc may have decelerated slip during the Maule earthquake and contributed to its nucleation. Furthermore, we infer that fluid saturated sediments inhibited significant slip close to the trench.

We study source processes of a large aftershock of the Maule sequence, the 2011 Mw 7.1 Araucania earthquake, by inverting local seismic waveforms for a multiple point-source faulting solution. We find this earthquake constituted rupture on the plate interface followed by almost instantaneous slip along a normal fault in the overriding plate: the first observation of its kind. The second rupture of this closely-spaced doublet was hidden from teleseismic faulting solutions, and may have been dynamically triggered by S-waves from the first event.

Overall, our work highlights the role played by the upper plate in subduction zone seismogenesis. We suggest that seismic velocities can help to characterise the behaviour of future large megathrust earthquakes. We show that the potential hazard posed by closely-spaced doublets involving the upper plate should be accounted for in real-time tsunami warning systems by using local waveform analysis.
University of Liverpool
Hicks, Stephen Paul
036d1b3b-bb7a-4a22-b2ce-71618a1723a3
Hicks, Stephen Paul
036d1b3b-bb7a-4a22-b2ce-71618a1723a3
Rietbrock, Andreas
e4656f22-06be-40fe-8f98-7f88c351c434
Ryder, Isabelle M.A.
e4db9c08-f27a-41a8-bbcc-0b6f9c472aad

Hicks, Stephen Paul (2015) Seismic properties and processes along the subduction plate interface: the February 2010 Mw 8.8 Maule, Chile earthquake. University of Liverpool, Doctoral Thesis, 253pp.

Record type: Thesis (Doctoral)

Abstract

The seismogenic zone of subduction margins has the potential to generate some of the world’s largest earthquakes. A detailed study of the 2010 Mw 8.8 Maule, Chile rupture has enabled interpretation of the controls that govern subduction zone seismic behaviour across the earthquake cycle. In this thesis, we focus on two aspects of the central Chile margin: (1) imaging physical properties in the forearc and along the plate interface; (2) assessing source complexity of megathrust ruptures.

We exploit a dataset of seismic body wave onset times from local aftershocks recorded on a temporary network to derive a 3-D seismic velocity model of the Maule rupture area. We image the main domains of the subduction zone and find a high velocity anomaly located along the plate interface, which we initially interpret as a subducted topographic high. We then develop a second, more accurate velocity model that uses an improved arrival time dataset together with observations from ocean-bottom seismometers. This refined model gives a sharper view of both the plate interface close to the trench, and the marine forearc. We show that ancient blocks of dense mantle in the lower forearc may have decelerated slip during the Maule earthquake and contributed to its nucleation. Furthermore, we infer that fluid saturated sediments inhibited significant slip close to the trench.

We study source processes of a large aftershock of the Maule sequence, the 2011 Mw 7.1 Araucania earthquake, by inverting local seismic waveforms for a multiple point-source faulting solution. We find this earthquake constituted rupture on the plate interface followed by almost instantaneous slip along a normal fault in the overriding plate: the first observation of its kind. The second rupture of this closely-spaced doublet was hidden from teleseismic faulting solutions, and may have been dynamically triggered by S-waves from the first event.

Overall, our work highlights the role played by the upper plate in subduction zone seismogenesis. We suggest that seismic velocities can help to characterise the behaviour of future large megathrust earthquakes. We show that the potential hazard posed by closely-spaced doublets involving the upper plate should be accounted for in real-time tsunami warning systems by using local waveform analysis.

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Hicks Aug 2015 - Version of Record
Available under License University of Southampton Thesis Licence.
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Published date: 2015

Identifiers

Local EPrints ID: 413252
URI: http://eprints.soton.ac.uk/id/eprint/413252
PURE UUID: 2d63ae2b-a802-454e-9915-d0ef8e5c743b
ORCID for Stephen Paul Hicks: ORCID iD orcid.org/0000-0002-7476-3284

Catalogue record

Date deposited: 18 Aug 2017 16:31
Last modified: 10 Mar 2022 18:24

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Contributors

Author: Stephen Paul Hicks ORCID iD
Thesis advisor: Andreas Rietbrock
Thesis advisor: Isabelle M.A. Ryder

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