Viscoelasticity modeling of clay minerals by dynamic viscoelasticity measurement and its implications for earthquake faulting

Abstract

Slip on clay fault planes at shallow depths in the seismogenic zone could be controlled by their rheology as well as their frictional properties; however, the rheological nature of clay faults is still an open question. Investigating the rheological properties of clay minerals is essential for understanding and modeling shallow earthquake faulting. Here, we perform dynamic viscoelasticity measurements on three clay minerals, namely kaolinite, illite, and smectite, wetted with water using a custom-made high pressure, high temperature rheometer. Our results confirm that the rheological properties resulting from the microstructure of clay minerals depend on the oscillation frequency, oscillation amplitude, temperature, and amount of water contained. In addition, the rheological properties vary systematically with the type of clay mineral. This suggests that the viscoelastic behavior of earthquake faults varies with the type of clay minerals present.