[S-CG43] Shallow and intermediate depth intraslab earthquakes: seismogenesis and rheology of the slab

[SCG43-P02] Viscoelastic behavior of solid-liquid two-phase under high pressure and high temperature

*Tomoya Muramoto^1,2, Yoshihiro Ito³, Noriyuki Furuichi² (1.Graduate school of faculty of science, Kyoto university, 2.National Metrology Institute of Japan, National Institute of Advanced Industrial Science and Technology, 3.Disaster Prevention Research Institute, Kyoto university)

Recently, slow slip events (SSEs) have been detected in various subduction zones around the world, and they have become an interesting subject of research as a universal physical phenomenon in subduction zones (Obara and Kato, 2016). In the subduction zone, it has become clear from observations that the mode of occurrence of various events such as SSEs changes with depth, and the cause of the change has been discussed from the viewpoint of material science and laboratory experiments. Material science viewing are also being incorporated into numerical studies in an explicit, among them, there is a growing number of parameter studies investigating the effect of viscoelasticity on the behavior of subduction zones. (e.g., Goswami and Barbot, 2018).
In this study, we aim to quantify the viscoelastic properties of various minerals in order to understand the mode of occurrence of various events such as SSEs and the phenomena that occur near the shallow part of subduction zones. Although experimental studies on the viscoelastic properties of solid (solid phase) and fluid (liquid phase) under the assumption of subduction zones have been actively conducted in recent years, the temperature and pressure dependence of viscoelastic properties of various minerals is still unknown. In this study, we performed a small amplitude oscillatory shear test (SAOS) at high pressure and high temperature to gain a basic understanding of the viscoelastic properties of various minerals.
The DHR (Waters Corp., e.g., Owens et al., 2020) was used for the measurements. The samples used were powdered and granular smectite, illite, quartz, and drilling cores acquired by the International Ocean Discovery Program (Saffer et al., 2019). The measurements revealed the amplitude and pressure dependence of the phase difference between strain and stress waveforms. Differences in the pressure dependence between minerals were also revealed. In addition, a decrease in shear stress due to a decrease in the viscosity of the liquid phase (Muramoto and Ito, under review) was also observed. The results obtained in this study on the amplitude and pressure dependence of the phase difference between strain and stress waveforms are complementary to the results obtained in previous friction experiments, and may reflect the stiffness of various minerals. In this presentation, we aim at a scale-free discussion by organizing the experimental results according to the appropriate parameter nondimensionalization performed by Jop et al. (2006) and Perrin et al. (2019), and we also discuss the amplitude and pressure dependence of the phase difference between strain and stress waveforms in terms of G' (elastic term) and G'' (viscous term) and the pressure dependence of the viscosity (Muramoto et al., 2020), and show the relationship between the amplitude of the strain waveform and the pressure coefficient based on the formulation.