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Dynamic rupture processes inferred from laboratory microearthquakes.

Passelègue, François. X. and Schubnel, Alexandre and Nielsen, Stefan and Bhat, Harsha S. and Deldicque, Damien and Madariaga, Raùl (2016) 'Dynamic rupture processes inferred from laboratory microearthquakes.', Journal of geophysical research : solid earth., 121 (6). pp. 4343-4365.

Abstract

We report macroscopic stick-slip events in saw-cut Westerly granite samples deformed under controlled upper crustal stress conditions in the laboratory. Experiments were conducted under triaxial loading (σ1>σ2=σ3) at confining pressures (σ3) ranging from 10 to 100 MPa. A high frequency acoustic monitoring array recorded particle acceleration during macroscopic stick-slip events allowing us to estimate rupture speed. In addition, we record the stress drop dynamically and we show that the dynamic stress drop measured locally close to the fault plane, is almost total in the breakdown zone (for normal stress > 75 MPa), while the friction f recovers to values of f > 0.4 within only a few hundred microseconds. Enhanced dynamic weakening is observed to be linked to the melting of asperities which can be well explained by flash heating theory in agreement with our post-mortem microstructural analysis. Relationships between initial state of stress, rupture velocities, stress drop and energy budget suggest that at high normal stress (leading to supershear rupture velocities), the rupture processes are more dissipative. Our observations question the current dichotomy between the fracture energy and the frictional energy in terms of rupture processes. A power law scaling of the fracture energy with final slip is observed over eight orders of magnitude in slip, from a few microns to tens of meters.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1002/2015JB012694
Publisher statement:Passelègue, F. X., A. Schubnel, S. Nielsen, H. S. Bhat, D. Deldicque, and R. Madariaga (2016), Dynamic rupture processes inferred from laboratory microearthquakes, Journal of Geophysical Research: Solid Earth, 121, 4343-4365, 10.1002/2015JB012694 (DOI). To view the published open abstract, go to http://dx.doi.org and enter the DOI.
Date accepted:23 April 2016
Date deposited:05 May 2016
Date of first online publication:11 June 2016
Date first made open access:No date available

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