講演情報
[S08-23]微弱な応力振動による粉体層のすべり誘発
坂本 龍之輔1、*波多野 恭弘1 (1. 大阪大学理学研究科宇宙地球科学専攻)
The phenomenon of transient strain from seismic waves triggering earthquakes is a robust observation. However, our understanding as to why seismic waves can trigger earthquakes remains incomplete. In this study, we use particle simulations to investigate the response of sheared granular matter to dynamic strain perturbations in order to better understand the dynamic triggering of earthquakes. In our simulation, an unstable slip is triggered when the dynamic strain above a threshold (critical strain) is applied to the system. We show that the critical strain is of the same order (10-6 to 10-9) as those in some experimental and observational studies. This enhanced response is observed at resonance wavelengths. Resonant vibration decreases the shear modulus of the granular system, and accordingly the shear strength is reduced, leading to unstable slip. This modulus softening is due to the increase in slipping contacts between particles. The relevance of simulation results to natural earthquake faults is discussed as to whether seismic waves can satisfy the resonance condition.