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Earthquake Nucleation Size: Evidence of Loading Rate Dependence in Laboratory Faults

Guérin‐Marthe, Simon; Nielsen, Stefan; Bird, Robert; Giani, Stefano; Di Toro, Giulio

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Authors

Simon Guérin‐Marthe

Dr Robert Bird robert.e.bird@durham.ac.uk
PDRA in Computational Solid Mechanics

Giulio Di Toro



Abstract

Recent GPS observations of major earthquakes such as the 2014 Chile megathrust show a slow pre‐slip phase releasing a significant portion of the total moment (Ruiz et al., 2014). Despite advances from theoretical stability analysis (Rubin & Ampuero, 2005; Ruina, 1983), and modeling (Kaneko, Carpenter, & Nielsen, 2017), it is not fully understood what controls the prevalence and the amount of slip in the nucleation process. Here we present laboratory observations of slow slip preceding dynamic rupture, where we observe a dependence of nucleation size and position on the loading rate (laboratory‐equivalent of tectonic loading rate). The setup is composed of two polycarbonate plates under direct shear with a 30 centimeters long slip interface. The results of our laboratory experiments are in agreement with the pre‐slip model outlined by Ellsworth and Beroza (1995) and observed in laboratory experiments (Latour, Schubnel, Nielsen, Madariaga, & Vinciguerra, 2013; Nielsen, Taddeucci, & Vinciguerra, 2010; Ohnaka & Kuwahara, 1990), which show a slow slip followed by an acceleration up to dynamic rupture velocity. However, further complexity arises from the effect of (1) rate of shear loading and (2) inhomogeneities on the fault surface. In particular, we show that when the loading rate is increased from 10−2 MPa.s−1 to 6 MPa.s−1, the nucleation length can shrink by a factor of three and the rupture nucleates consistently on higher shear stress areas. The nucleation lengths measured fall within the range of the theoretical limits Lb and L∞ derived by Rubin and Ampuero (2005) for rate‐and‐state friction laws.

Citation

Guérin‐Marthe, S., Nielsen, S., Bird, R., Giani, S., & Di Toro, G. (2018). Earthquake Nucleation Size: Evidence of Loading Rate Dependence in Laboratory Faults. Journal of Geophysical Research. Solid Earth, 124(1), 689-708. https://doi.org/10.1029/2018jb016803

Journal Article Type Article
Acceptance Date Dec 13, 2018
Online Publication Date Dec 16, 2018
Publication Date Jan 1, 2018
Deposit Date Jan 4, 2019
Publicly Available Date Feb 26, 2019
Journal Journal of Geophysical Research. Solid Earth
Print ISSN 2169-9313
Electronic ISSN 2169-9356
Publisher American Geophysical Union
Peer Reviewed Peer Reviewed
Volume 124
Issue 1
Pages 689-708
DOI https://doi.org/10.1029/2018jb016803

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Publisher Licence URL
http://creativecommons.org/licenses/by/4.0/

Copyright Statement
Advance online version © 2018. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.




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