Avalanches in anisotropic sheared granular media

TL;DR

This study investigates how particle shape anisotropy affects avalanches in sheared granular media, revealing that while avalanche size remains shape-independent, aftershock sequences and occurrence probabilities are significantly influenced by anisotropy.

Contribution

It demonstrates the impact of particle anisotropy on avalanche dynamics and aftershock behavior, providing a new way to infer microscopic particle properties from macro-scale avalanche sequences.

Findings

Avalanche magnitude aligns with Gutenberg-Richter law regardless of particle shape.

Aftershock sequences are strongly affected by particle anisotropy, altering Omori's law exponent.

Particle anisotropy influences the probability of avalanche occurrence based on stiffness and friction.

Abstract

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.