(NAS Colloquium) Earthquake Prediction The Scientific Challenge (1996) / Chapter Skim
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The organization of seismicity on fault networks
The organization of seismicity on fault networks
Pages 3830-3837
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From page 3830... ...
There is no validity to the popular assumption that the average rate of slip on individual faults is a constant. Intermediate term precursory activity such as local quiescence and increases in intermediate-magnitude activity at long range are simulated well by the assumption that strong weakening of faults by injection of fluids and weakening of asperities on inhomogeneous models of fault networks is the dominant process; the heat flow paradox, the orientation of the stress field, and the low average stress drop in some earthquakes are understood in terms of the asperity model of inhomogeneous faulting.
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From page 3831... ...
The Influence of Geometry We turn to inhomogeneous faults or fault zones as systems with intrinsic scale sizes to explore the differences between large 250 200 a)
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Because of the correlations between fracture strengths in the model, a region of large fracture strength can store large amounts of potential energy that will be released in large earthquakes; sites with large fracture stresses require a greater time for restoration of the stress to the fracture threshold from plate tectonic sources than do those with small thresholds. The larger events have greater stress drops than do the small ones in these models with fractal distributions of thresholds, a result that is not wholly consistent with observation, thus suggesting that this fractal barrier model is inappropriate for the description of large earthquakes.
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From page 3833... ...
A spiky distribution of fracture strengths, intended to simulate a sparse distribution of barriers on a single fault, leads to a very different display of space-time seismicity, from the preceding case (Fig.
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From page 3834... ...
A cumulative distribution of the interval times is fit well by a truncated exponential distribution (Fig. 6~: there are no interval times less than a certain critical value; the upper end of the distribution is terminated by the values for the extended lacunae, which are evidently inconsistent with the exponential distribution.
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From page 3835... ...
and has been used in studies of self-organization on extended single faults (60-63~. The presence of water vastly accelerates the rate of weakening of strength of fault materials and especially so at elevated temperatures because the weakening follows an activation process; it is the accelerated weakening that makes this process competitive in the intermediate time scale.
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From page 3836... ...
The model of a fluidized fault network, sutured by occasional asperities, can explain the heat flow paradox, the orientation of the stress field near the SAF, and the low average stress drop in some strong earthquakes. This research was supported by a grant from the Southern California Earthquake Center.
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From page 3837... ...
38. Working Group on California Earthquake Probabilities (1995)
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