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Nonlinear Processes in Geophysics An interactive open-access journal of the European Geosciences Union

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Nonlin. Processes Geophys., 21, 763-775, 2014
https://doi.org/10.5194/npg-21-763-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
24 Jul 2014
Complex networks and waveforms from acoustic emissions in laboratory earthquakes
H. O. Ghaffari1, B. D. Thompson2, and R. P. Young1 1Department of Civil Engineering and Lassonde Institute, University of Toronto, Toronto, 170 College Street, M5S 3E3, ON, Canada
2Mine Design Engineering, 1045 John Counter Boulevard, Kingston, ON K7K 6C7, Canada
Abstract. Understanding the physics of acoustic excitations emitted during the cracking of materials is one of the long-standing challenges for material scientists and geophysicists. In this study, we report novel results of applications of functional complex networks on acoustic emission waveforms emitted during the evolution of frictional interfaces. Our results show that laboratory faults at microscopic scales undergo a sequence of generic phases, including strengthening, weakening or fast slip and slow slip, leading to healing. For the first time we develop a formulation on the dissipated energy due to acoustic emission signals in terms of short-term and long-term features (i.e., networks' characteristics) of events. We illuminate the transition from regular to slow ruptures. We show that this transition can lead to the onset of the critical rupture class similar to the direct observations of this phenomenon in the transparent samples. Furthermore, we demonstrate the detailed submicron evolution of the interface due to the short-term evolution of the rupture tip. As another novel result, we find that the nucleation phase of most amplified events follows a nearly constant timescale, corresponding to the initial strengthening or locking of the interface. This likely indicates that a thermally activated process can play a crucial role near the moving crack tip.

Citation: Ghaffari, H. O., Thompson, B. D., and Young, R. P.: Complex networks and waveforms from acoustic emissions in laboratory earthquakes, Nonlin. Processes Geophys., 21, 763-775, https://doi.org/10.5194/npg-21-763-2014, 2014.
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