[S-SS10] 地震発生の物理・断層のレオロジー

[SSS10-16] The Impact of Medium Heterogeneity on Earthquake Cycles Based on Numerical Modelling

*Xu Sun¹、Zhenguo Zhang¹ (1.Department of Earth and Space Sciences, Southern University of Science and Technology, Shenzhen, China)

キーワード：Medium Heterogeneity, Earthquake Cycles

The environments in which earthquakes occur exhibit significant complexity, with subsurface media typically demonstrating three-dimensional heterogeneity. Extensive research has demonstrated that heterogeneous media can influence earthquake nucleation and long-term fault evolution. Therefore, investigating the effects of medium heterogeneity on earthquake cycles is crucial for understanding the underlying physical mechanisms of fault behavior. Using a finite difference method, we simulated earthquake cycles on a two-dimensional subduction zone fault with laterally stratified media along the strike direction. Our simulations revealed distinct patterns: in homogeneous media, earthquakes nucleate alternately at both ends of the fault, whereas when the medium is stratified into high and low S-wave velocity layers along the strike, earthquake events predominantly nucleate in the high-velocity layer, with only small earthquakes occurring in the low-velocity layer. This phenomenon arises because higher S-wave velocities correspond to greater shear modulus, leading to shorter earthquake recurrence intervals. Notably, in homogeneous media, regions where ruptures terminate tend to accumulate residual high stress and subsequently become nucleation sites for new earthquakes. However, when ruptures terminate within low-velocity layers, the inherently lower stress state in these regions prevents subsequent earthquake nucleation. These findings collectively indicate that low-velocity media exert an inhibitory effect on occurrence of earthquakes.