Earthquakes at the lab scale and their memory effect

We study an experimental reproduction of a seismic fault by submitting a granular sample of glass beads to a biaxial test and looking at the stationary phase following the deformation's localisation into shear bands. A technique based on interferometry allows us to measure the local deformation occurring in the sample. We observe fluctuation of the plasticity inside the shear bands, similar to the way earthquakes occur along  seismic fault lines. In both cases, the total displacement is the accumulation of the individual slip of each event. The spatio-temporal dynamics of these lab-scale earthquakes follow the same statistical properties as real ones. Indeed, the amplitude distribution of the events follows a power law with the same exponent as the Gutenberg-Richter law[1]. We also observe that lab-earthquakes tend to cluster together in time and space forming aftershock sequences which follow Omori's law.

In my talk, I will present recent experimental results where we investigated the effect of the strain rate we impose on our sample on the memory effect we observe[2]. We showed that the aftershock sequences are driven by deformation and not time. I will also discuss a cellular automaton model reproducing this behaviour.