Common dependence on stress for the statistics of granular avalanches and earthquakes.
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The faulting style dependence may be related to the magnitude of the differential stress, but no model so far has been able to reproduce this behaviour.Here we investigate the statistical properties of avalanches in a dissipative, bimodal particulate system under slow shear.These results are consistent with recent seismological observations of earthquake size-distribution and aftershock statistics.
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Affiliation: Earthquake Research Institute, University of Tokyo, 113-0032 Tokyo, Japan.
ABSTRACT
Both earthquake size-distributions and aftershock decay rates obey power laws. Recent studies have demonstrated the sensibility of their parameters to faulting properties such as focal mechanism, rupture speed or fault complexity. The faulting style dependence may be related to the magnitude of the differential stress, but no model so far has been able to reproduce this behaviour. Here we investigate the statistical properties of avalanches in a dissipative, bimodal particulate system under slow shear. We find that the event size-distribution obeys a power law only in the proximity of a critical volume fraction, whereas power-law aftershock decay rates are observed at all volume fractions accessible in the model. Then, we show that both the exponent of the event size-distribution and the time delay before the onset of the power-law aftershock decay rate are decreasing functions of the shear stress. These results are consistent with recent seismological observations of earthquake size-distribution and aftershock statistics. No MeSH data available. Related in: MedlinePlus |
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Mentions: First, we discuss the nature of the avalanche magnitude-frequency distribution with respect to the two control parameters, the shear rate and the volume fraction ϕ. Figure 3a,b show these distributions at several shear rates for ϕ = 0.644 and ϕ = 0.650, respectively. Both parameters control the shape of the magnitude-frequency distribution. For example, one can observe a break in scale-invariance for high shear rates at low volume fraction (ϕ = 0.644 and in Fig. 3a). Similarly, characteristic-size distribution (i.e, peaked at a single magnitude) are observed for high volume fraction (Fig. 3b). However, the distribution is independent of the shear rate below a characteristic -value, which may be interpreted as the inverse of the structural relaxation time. Not surprisingly, this threshold value is a decreasing function of the volume fraction. In the volume fraction range investigated here, it is approximately 10−6 for ϕ = 0.644 (Fig. 3a) and 10−8 for ϕ = 0.650 (Fig. 3b). Hereafter, we discuss such rate-independent behaviours by choosing sufficiently low shear rates. |
View Article: PubMed Central - PubMed
Affiliation: Earthquake Research Institute, University of Tokyo, 113-0032 Tokyo, Japan.
No MeSH data available.