MasterNanosciences, nanotechnologies

Context and objectives

A seismic fault is formed by two rock faces in contact, pressed and sheared by tectonic movements. The fault is generally locked, held in place by friction between the faces. However, when the shear loading becomes large, the fault experiences rapid sliding events, which are at the origin of earthquakes. Sliding events consist of an interfacial rupture propagating along the seismic fault, whose role is to weaken the solid contacts that resist to shear. How these ruptures are initiated, how they propagate and what controls their dynamics are crucial questions for understanding the seismic cycle of faults and for defining strategies for monitoring faults.
More generally, the onset of sliding of two solids in contact, not only rock faces, is mediated by the propagation of an interfacial rupture. For simple systems of two solids in contact, these ruptures are shear cracks as described by the brittle fracture theory [1]. However, seismic faults are much more complex, with cores that are often composed of granular materials, known as gouge layers. How interfacial ruptures propagate within a gouge layer has not been experimentally investigated yet. The aim of this project is to study how the nature and the dynamics of the interfacial rupture are affected when propagating through a granular fault core.

 Methods and expected results

The approach is experimental, building up on a setup that has been previously developed, that consists in two sheared elastic solids sandwiching a granular material [2]. During this project, the fault’s mechanical response to shear will be measured via the measurement of macroscopic forces, and local measurements will be performed along the fault: high-frequency strain measurements and particle tracking within the gouge layer. These measurements will allow 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.

Scientific field: Solid friction; Fracture; Fault mechanics
Experimental methods: Strain measurements; High-speed imaging and image analysis 

Expected skills

This internship is devoted to a student of the GS program Soft Nanosciences  following the master Physics of Complex Systems  or the master Applied Mechanics.

Bibliography

[1] I. Svetlizky, E. Bayart, and J. Fineberg, Annu. Rev. Condens. Matter Phys. 10, 253 (2019).
[2] Y. Faure and E. Bayart, Nature Communications 15, 8217 (2024)