In-situ X-ray imaging of stick-slip behavior in small-scale polystyrene fault analogs

Understanding the mechanisms controlling fault slip requires dedicated experimental setups that bridge the gap between natural conditions and observable scales. These experiments may require the use of analogue materials adapted to the scale of the laboratory, which present interesting characteristics facilitating the observation of physical processes. Polystyrene, due to its low strength and elastic properties, and structure, offers an effective analog material to investigate mechanical fault processes at both large (metric) and small scales (cm). Its low elastic properties slows down deformation processes and enables in-situ small scale observations using X-ray microCT.

In this study, we performed uniaxial compression experiments on small polystyrene blocks with a pre-cut slip interface. Polystyrene of various initial densities were tested. Compression rates ranged from 0.1 to 1 mm/min to induce different slip modes, from slow slip to dynamic stick-slip events. Real-time 2D X-ray radiography was coupled with mechanical monitoring to capture the onset and evolution of slip along the interface. Additionally, 3D scans were acquired at various stages during compression, with the objective of evaluating the spatial distribution of deformation around the fault plane over time.

The aim of this study is to combine mechanical data and imaging in order to characterize internal density changes associated with deformation. Preliminary observations seem to highlight density contrasts in the bulk material around the fault plane, offering insight into potential precursory signs of slip.

This approach demonstrates the potential of X-ray microCT for high-resolution monitoring of analog fault models, with perspectives for quantifying strain localization and post-slip damage patterns. These results may contribute to the understanding of frictional behavior and rupture dynamics in scaled experiments.