ABSTRACT

A many-body disk model of slip phenomena was investigated as a model for earthquake faulting. There is a boundary layer between slip surfaces, i.e., fault clay and fault gouge in a case of earthquake faults. Although mechanical properties of these boundary layers play an important role in fault sliding, the actual fault gouge is too complicated to understand its essential role. Two-dimensional many-body disks were used as a boundary layer. Acrylic resin cylinders were packed as disks into the annular cell that consisted of the outer rotating cylinder and the inner fixed cylinder. The stick-slip events were observed in the time series of torque measured at the inner cylinder. The size distributions of stick-slip events obey a power law, indicating an analogy between the model and the earthquake faulting, because the earthquake size distribution is also a power law distribution known as Gutenberg-Richter law. An elementary process of the model, i.e. behavior of individual disk, can be observed by using a CCD video camera recorder. This enables us to observe microscopic behavior (each disk behavior) during such macroscopic behaviors as a 1/f fluctuation and a power law size distribution. We discussed an analogy between the behavior of the model and earthquakes. It was suggested that it would give us an important clue for understanding sliding of earthquake faults as a self-organized criticality.