  We study the influence of particle shape anisotropy on the occurrence of
avalanches in sheared granular media. We use molecular dynamic simulations to
calculate the relative movement of two tectonic plates. % with transform
boundaries. Our model considers irregular polygonal particles constituting the
material within the shear zone. We find that the magnitude of the avalanches is
approximately independent on particle shape and in good agreement with the
Gutenberg-Richter law, but the aftershock sequences are strongly influenced by
the particle anisotropy yielding variations on the exponent characterizing the
empirical Omori's law. Our findings enable one to identify 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 a significant influence of the particle anisotropy.
