Seismicity in a model governed by competing frictional weakening and healing mechanisms

Abstract

S U M M A R YObservations from laboratory, field and numerical work spanning a wide range of space and time scales suggest a strain dependent progressive evolution of material properties that control the stability of earthquake faults. The associated weakening mechanisms are counterbalanced by a variety of restrengthening mechanisms. The efficiency of the healing processes depends on local material properties and on rheologic, temperature, and hydraulic conditions. We investigate the relative effects of these competing non-linear feedbacks on seismogenesis in the context of evolving frictional properties, using a mechanical earthquake model that is governed by slip weakening friction. Weakening and strengthening mechanisms are parametrized by the evolution of the frictional control variable-the slip weakening rate R-using empirical relationships obtained from laboratory experiments. In our model, weakening depends on the slip of an earthquake and tends to increase R, following the behaviour of real and simulated frictional interfaces. Healing causes R to decrease and depends on the time passed since the last slip. Results from models with these competing feedbacks are compared with simulations using non-evolving friction. Compared to fixed R conditions, evolving properties result in a significantly increased variability in the system dynamics. We find that for a given set of weakening parameters the resulting seismicity patterns are sensitive to details of the restrengthening process, such as the healing rate b and a lower cutoff time, t c , up to which no significant change in the friction parameter is observed. For relatively large and small cutoff times, the statistics are typical of fixed large and small R values, respectively. However, a wide range of intermediate values leads to significant fluctuations in the internal energy levels. The frequency-size statistics of earthquake occurrence show corresponding non-stationary characteristics on time scales over which negligible fluctuations are observed in the fixed-R case. The progressive evolution implies that-except for extreme weakening and healing rates-faults and fault networks possibly are not well characterized by steady states on typical catalogue time scales, thus highlighting the essential role of memory and history dependence in seismogenesis. The results suggest that an extrapolation to future seismicity occurrence based on temporally limited data may be misleading due to variability in seismicity patterns associated with competing mechanisms that affect fault stability.

Temporal variation in fault friction and its effects on the slip evolution of a thrust fault over several earthquake cycles

“…Finally, our results show that small changes in the friction coefficient can easily explain deviations from the periodic earthquake recurrence model without the need of assuming either a temporally constant failure stress (time‐predictable model) or a coseismic stress drop to a temporally constant level (slip‐predictable model). This finding is consistent with the study by Hillers et al. (2009), who observed in 1D numerical experiments that frictional weakening and healing significantly increase the variability in earthquake frequency and size.…”

“…, 2007). One‐dimensional numerical models showed that the competition between frictional weakening and healing cause considerable variability in the frequency‐size distribution of earthquakes (Hillers et al. , 2009).…”

Laboratory observations of time‐dependent frictional strengthening and stress relaxation in natural and synthetic fault gouges

“…The evolution of fault strength during the seismic cycle exerts an important control on earthquake size and recurrence [Hiller et al, 2009;De Paola et al, 2012;Hampel and Hetzel, 2012;McLaskey et al, 2012]. In order for a fault (or fault patch) to undergo repeated earthquake failure, it must have the ability to restrengthen during the interseismic period [Brace and Byerlee, 1966;Brace, 1972;Dieterich, 1972Dieterich, , 1978.…”

Study on Simulation of Foreshock Activity Properties before Strong Earthquake Using Heterogeneous Cellular Automata Models

“…We uses a cellular automata model composed by cell (the unit of system) and evolution rule after comparing previous research works [10]- [18].…”