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Soutenance de Yohann Faure

Influence of a granular media on the dynamics of a lab tectonic fault
When Jul 17, 2024
from 02:00 to 04:00
Where Salle des thèses
Contact Name Yohann Faure
Attendees Yohann Faure
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When two tectonic plates in contact move relative to each other, an increasing shear forceis applied to their interface, the seismic fault, which eventually starts slipping, giving rise to anearthquake that releases the stored elastic energy. The study of these movements on a globalscale is carried out in situ using seismic or geodetic measurements, but as well as being highlyheterogeneous, the interfaces studied are not directly accessible. Laboratory experiments can beused to study the behaviour of model faults formed by samples of rocks or plastic materials byisolating the parameters that play a role in their dynamics. The aim of our study is to identifythe influence of a layer of gouge, a crushed rock present at the interface in powder or grainform, on the behaviour of a seismic fault.To do this, we developed an experimental device for shearing a frictional interface, enablingus to measure deformations and track particles at high frequency. This allowed us to performvarious experiments on two-dimensional frictional interfaces formed by solid blocks of PMMA inthe presence of a granular medium trapped at the interface, modelling the gouge. In particular,we studied the interaction mechanisms between a slowly slipping portion of a fault and thesurrounding locked regions. Our results show that the slowly slipping portion acts as a precursorto rupture events, destabilising the interface by a mechanism similar to that of a pre-crack ina homogeneous solid. This result and this versatileexperimental set-up pave the way for newperspectives in the study of complex frictional interfaces.