Investigating the Propagation of Frictional Ruptures in GranularMedia
Post-doc
The onset of frictional motion is mediated by the propagation of interfacial ruptures, which are at the origin of earthquakes when they occur along seismic faults. The failure mechanisms of a simple frictional interface – formed by two intact solids in contact – are now well understood and experimentally characterised. Such propagative ruptures are shear cracks, as described by fracture mechanics. This framework is widely used in numerical models of earthquakes. However, seismic faults are far more complex, with their cores often composed of granular materials, known as gouge layers.
The aim of this project is to investigate how the nature and the dynamics of the interfacial rupture are affected when propagating through such granular fault cores, an area that has not yet been experimentally investigated. This study will build on a setup that has been previously developed, consisting of two sheared elastic solids sandwiching a granular material. We will examine the fault’s mechanical response to shear by measuring macroscopic forces, and we will perform local measurements along the fault, namely highfrequency strain measurements and particle tracking within the gouge layer. These measurements will allow us to characterize the dynamic strain fields that drive the rupture propagation and to compute the associated energy budget, providing an understanding of the factors that control rupture dynamics.
To complement these experiments, we will develop a numerical model that simulates the elastic behaviour of the solid plates and the shear response of the granular gouge. Initial tests will validate the model's ability to generate propagative ruptures.
By studying the effect of a granular material on rupture propagation, this project aims to provide a better understanding of the rupture mechanisms that cause earthquakes. The results will allow to account for fault composition in earthquake models, thereby advancing seismic risk assessment and mitigation strategies. Additionally, our work will enable the identification of key physical quantities that characterise the fault composition, with the aim of being able to extract these quantities from field data, thereby improving fault monitoring. This work represents a critical step towards more accurate earthquake modeling and better informed mitigation strategies.
