We study rapidly accelerating rupture fronts at the onset of frictional motion by performing high-temporal-resolution measurements of both the real contact area and the strain fields surrounding the propagating rupture tip. We observe large-amplitude and localized shear stress peaks that precede rupture fronts and propagate at the shear-wave speed. These localized stress waves, which retain a well-defined form, are initiated during the rapid rupture acceleration phase. They transport considerable energy and are capable of nucleating a secondary supershear rupture. The amplitude of these localized waves roughly scales with the dynamic stress drop and does not decrease as long as the rupture front driving it continues to propagate. Only upon rupture arrest does decay initiate, although the stress wave both continues to propagate and retains its characteristic form. These experimental results are qualitatively described by a self-similar model: a simplified analytical solution of a suddenly expanding shear crack. Quantitative agreement with experiment is provided by realistic finiteelement simulations that demonstrate that the radiated stress waves are strongly focused in the direction of the rupture front propagation and describe both their amplitude growth and spatial scaling. Our results demonstrate the extensive applicability of brittle fracture theory to fundamental understanding of friction. Implications for earthquake dynamics are discussed.
|Original language||American English|
|Number of pages||6|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - 19 Jan 2016|
Bibliographical noteFunding Information:
We thank G. Cohen for fruitful discussions. This work was supported by James S. McDonnell Fund Grant 220020221, European Researc Council Grant 267256, and Israel Science Foundation Grants 76/11 and 1523/15 (all to I.S. and J.F.); European Research Council Grant ERCstg UFO-240332 (to J.-F.M., D.S.K., and D.P.M.); and Swiss National Science Foundation Grant PMPDP2-145448 (to M.R.). This work was also supported by Cornell University (D.S.K.).
- Acoustic radiation
- Earthquake dynamics
- Nonsteady rupture dynamics
- Seismic radiation