Slow-slip, slow earthquakes, period-two cycles, full and partial ruptures, and deterministic chaos in a single asperity fault

By Sylvain Barbot. Tectonophysics, 2019

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Abstract The assimilation of geological, geophysical, and laboratory data in physics-based models of fault dynamics promises increasingly realistic simulations of the seismic cycle. To assist this effort, I explore the dynamics of a single velocity-weakening asperity to delineate the relationship between a fault physical properties and the style of faulting during the seismic cycle based on a micro-physical model of rate-and-state friction. From a dimensional analysis, four non-dimensional parameters control the characteristics of slip events and the behavior during the interseismic period, including the Dieterich-Ruina-Rice number Ru, which is proportional to the ratio of asperity to critical nucleation size W/h*, and Rb = (b − a)/b, where a and b control the direct and local evolutionary effects, respectively. For sufficiently large Rb, the Ru number controls the spectrum of fault slip, from periodic slow-slip events to aperiodic fast ruptures. In finite faults, but not in semi-infinite faults, the transition between these end-members includes a bifurcation that involves period-two, period-four, period-six cycles, and deterministic chaos with increasing Ru. Macroscopic fault slip is stabilized as Rb vanishes, even as Ru ≫ 1. For finite faults, but not for semi-infinite faults, the transition between slow and fast ruptures for increasing Rb includes another type of bifurcation with period-two and period-four cycles of slow and fast ruptures. For 0

Subfields: Geophysics

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