Pulselike Ruptures on Strong Velocity-Weakening Frictional Interfaces: Dynamics and Implications

Citation

Elbanna, Ahmed Ettaf (2011) Pulselike Ruptures on Strong Velocity-Weakening Frictional Interfaces: Dynamics and Implications. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/80MV-6Y66. https://resolver.caltech.edu/CaltechTHESIS:12122010-174517720

Abstract

Seismic inversion and computational models have shown that earthquake ruptures may propagate in one of two basic modes; the cracklike mode and the slip pulse mode. In this work we use analytical and numerical techniques to study the dynamics and implications of pulselike ruptures propagating on strong velocity-weakening frictional interfaces using both discrete and continuum models of fracture.

Results of the study of the discrete spring block slider model suggest that strong velocity-weakening friction might yield to the propagation of unsteady slip pulses and chaotic dynamics. The prestress in most of these systems evolves into very heterogeneous spatial distributions characterized, in general, by non-Gaussian statistics and power-law spectral properties. It is also shown that the combined effect of slip pulse propagation and strong velocity-weakening friction could yield to size effects in strength with the strength decreasing as a power law with increasing rupture length.

By examining the energy budget of slip pulses in the discrete model, we show that it is possible to derive a nonlinear differential equation that could predict the final slip distribution in an event, given the prestress existing before that event and some information about friction and pulse dynamics. The equation is successful in replicating many of the macroscopic slip features, including the slip distribution and total rupture length, can also match many long-time statistics regarding the prestress evolution and the event size distribution.

Results from the continuum study suggest that the absence of steady pulses in previous studies could be attributed to the details of the nucleation procedure. We show that steady pulses could exist on strong velocity-weakening friction and uniform prestress if both the prestress and nucleation procedures are correctly tuned. We find that steady pulses are unstable to perturbations in the form of a step in the prestress and could arrest quickly in regions of low prestress. Steady pulses are also found to adapt well to local fluctuations in the prestress, leading to heterogeneous slip distributions. This result might have important implications for the problem of slip complexity in real earthquakes.

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