Role of visco-elastic rheologies in the persistence of heterogeneous stress distributions in dynamic rupture models.

Understanding how past ruptures will affect the propagation of the following ruptures is fundamental to a better comprehension of earthquake behavior. In that sense, numerical simulations provide a useful tool to study the dynamics of slip. In this study, we model a setup similar to laboratory friction experiments [Rubinstein et al., 2007; Ben-David et al. 2010], consisting of a 2D block of viscoelastic material in contact with a rigid body, with slip-weakening friction at the interface. As in the experiments, the block is loaded from the side, which results in a high concentration of shear stresses close to one edge, where slip will initiate. We observe a sequence of precursory slip, which initiate at shear levels well below the global static friction threshold. These precursory slip stop before propagating over the entire interface, and their length increase with increasing loading. High stress concentrations are generated at the tip of the arrested rupture. We analyze the evolution of these stress concentrations when the following slip events take place. Due to the viscous properties of the material, the stress concentrations created by the arrest of precursory slip are not erased by the propagation of the following rupture, but reappear with the relaxation of the material, with a smaller amplitude. This leads to perturbation in the rupture velocities, with accelerations of the front at the location of these stress concentrations. The amplitude of the stress concentrations follows an exponential decrease rate with successive ruptures. We show that this decrease rate is controlled by the material properties, in particular the ratio of the viscous over instantaneous Young’s moduli. Our formulation gives a good agreement to the behavior observed in the simulations, and implies that about five slip fronts are necessary to erase all stress concentrations. These results highlight the importance of viscous relaxation mechanisms in the persistence of heterogeneous stress state along a frictional interface. This study also provides a mechanism to explain how previous slip history will influence the propagation of the next rupture.

Presented at:
American Geophysical Union Fall Meeting, San Francisco, California, USA, 2010., December 9-13, 2013

 Record created 2014-01-14, last modified 2018-03-17

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