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Avalanches in anisotropic sheared granular media

By: Andres Pena
From: Bilfinger Berger, Wiesbaden, Germany
At: Complexo Interdisciplinar, Anfiteatro
[2009-03-25] 12:00

We study the influence of particle shape anisotropy on the occurrence of avalanches in sheared granular media. To this end, we use molecular dynamic simulations to mimic the relative movement of two tectonic plates with transform boundaries. Our model considers irregular polygonal particles as constituent of the material within the shear zone. We find that the magnitude of the avalanches is in good agreement with the Gutenberg-Richter law and independent of particle shape, but the aftershock sequences are strongly influenced by the particle anisotropy yielding a possible explanation for the variation of the decay on the empirical Omori law. Our findings raise the possibility of identifying the presence of anisotropic particles at the macro-mechanical level only by observing the avalanche sequences of real faults. In addition, we calculate the probability of occurrence of an avalanche for given values of stiffness or frictional strength and observe also significant influence of the particle anisotropy.