Dynamic rupture processes inferred from laboratory microearthquakes

Passelègue, François. X.; Schubnel, Alexandre; Nielsen, Stefan; Bhat, Harsha S.; Deldicque, Damien; Madariaga, Raùl

doi:10.1002/2015jb012694

Dynamic rupture processes inferred from laboratory microearthquakes

Passelègue, François. X.; Schubnel, Alexandre; Nielsen, Stefan; Bhat, Harsha S.; Deldicque, Damien; Madariaga, Raùl

Authors

François. X. Passelègue

Alexandre Schubnel

Professor Stefan Nielsen stefan.nielsen@durham.ac.uk
Professor

Harsha S. Bhat

Damien Deldicque

Raùl Madariaga

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.

Citation

Passelègue, F. X., Schubnel, A., Nielsen, S., Bhat, H. S., Deldicque, D., & Madariaga, R. (2016). Dynamic rupture processes inferred from laboratory microearthquakes. Journal of Geophysical Research. Solid Earth, 121(6), 4343-4365. https://doi.org/10.1002/2015jb012694

Journal Article Type	Article
Acceptance Date	Apr 23, 2016
Online Publication Date	Jun 11, 2016
Publication Date	Jun 11, 2016
Deposit Date	May 4, 2016
Publicly Available Date	Dec 11, 2016
Journal	Journal of Geophysical Research. Solid Earth
Print ISSN	2169-9313
Electronic ISSN	2169-9356
Publisher	American Geophysical Union
Peer Reviewed	Peer Reviewed
Volume	121
Issue	6
Pages	4343-4365
DOI	https://doi.org/10.1002/2015jb012694

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Copyright Statement
Advance online version 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.