In this study, the role of fluids in a slow slip events (SSEs) regime
was examined by investigating the rheological properties of the
solid-liquid two-phase system on a laboratory scale. We specifically
investigated how the rheological properties change with the shear rate
when the granular layer is fluid-rich. We used a velocity-controlled
rheometer to apply shear to a liquid-saturated granular layer. The
results show that the liquid-saturated granular layer’s shear viscosity
depended on the liquid viscosity and exhibited pseudoplastic behavior.
Additionally, the saturated granular layered exhibited hysteresis, which
increased as the viscosity of the liquid decreased. After a quantitative
discussion through Bagnold (1954) framework, we propose a fault model
that includes a fluid-rich granular layer.