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Megathrust friction determined from mechanical analysis of the forearc in the Maule earthquake area

Cubas, Nadaya and Avouac, Jean-Philippe and Souloumiac, Pauline and Leroy, Yves (2013) Megathrust friction determined from mechanical analysis of the forearc in the Maule earthquake area. Earth and Planetary Science Letters, 381 . pp. 92-103. ISSN 0012-821X. http://resolver.caltech.edu/CaltechAUTHORS:20131220-080054379

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Abstract

The seismogenic potential of a given fault depends essentially on its frictional properties and on the mechanical properties of the medium. Determining the spatio-temporal variations of frictional properties is therefore a key issue in seismotectonics. This study aims to characterize the friction on the South America megathrust in the 2010 Mw 8.8 Maule earthquake area from mechanical analysis of the forearc structure and morphology. Based on the critical taper theory, we first show that the rupture area of the Maule earthquake, also shown to be locked in the interseismic period, coincides with the stable part of the wedge. In the surrounding area, the wedge is critical, a finding consistent with various evidence for active deformation there. This is in particular true for the Arauco Peninsula area which seems to have arrested the Maule earthquakeʼs rupture to the South. This observation lends support to the view that the seismic rupture is inhibited when propagating beneath a critical area. The geometry of the critical portion of the wedge suggests a standard internal friction (μ_(int)=0.7±0.13) and a hydrostatic pore pressure within the wedge. The effective friction beneath the critical outer wedge is estimated to be µ^(eff)_b = 0.7 ± 0.13. This could be related to intrinsically low friction minerals (clay) or high pore pressure along the megathrust. We next use the limit analysis approach to constrain the variation of the effective friction along the megathrust based on the location and geometry of internal faulting within the forearc. A low effective friction is found within the rupture area (µ^(eff)_b ≤ 0.14) to explain the reactivation of thrust fault such as the Santa Maria, updip of the coseismic rupture, or the activation of normal splay faults downdip of the rupture area. The low effective friction found there could reflect strong dynamic weakening.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.epsl.2013.07.037DOIArticle
http://www.sciencedirect.com/science/article/pii/S0012821X13004329PublisherArticle
Additional Information:© 2013 Elsevier B.V. Received 8 March 2013. Received in revised form 25 July 2013. Accepted 29 July 2013. Available online 25 September 2013. Editor: P. Shearer. This project was supported by the by the National Science Foundation through grant EAR-#1118239 and by the Gordon and Betty Moore Foundation through Grant GBMF #423.01 to the Caltech Tectonics Observatory. This is Tectonics Observatory contribution #236.
Group:Caltech Tectonics Observatory, Seismological Laboratory
Funders:
Funding AgencyGrant Number
NSFEAR-1118239
Gordon and Betty Moore FoundationGBMF 423.01
Subject Keywords: Maule earthquake; frictional properties; dynamic weakening; critical wedge
Other Numbering System:
Other Numbering System NameOther Numbering System ID
Caltech Tectonics Observatory236
Record Number:CaltechAUTHORS:20131220-080054379
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20131220-080054379
Official Citation:Nadaya Cubas, Jean-Philippe Avouac, Pauline Souloumiac, Yves Leroy, Megathrust friction determined from mechanical analysis of the forearc in the Maule earthquake area, Earth and Planetary Science Letters, Volume 381, 1 November 2013, Pages 92-103, ISSN 0012-821X, http://dx.doi.org/10.1016/j.epsl.2013.07.037. (http://www.sciencedirect.com/science/article/pii/S0012821X13004329)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43105
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:20 Dec 2013 16:38
Last Modified:11 Jun 2015 13:57

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