1Simulation of Complex Recurrence Behavior of Earth- quakes with an Interacting Fault System Model

Activity of large earthquakes in and around the Japanese Islands is simulated with a model that incorporates mechanical interactions between faults, including both interplate and intraplate faults. In this simulation, each fault element is as-sumed to accumulate stress with a constant slip deficit rate and redistribute its accumulated stress to surrounding faults by making a forward (coseismic) slip when the cumulative stress reaches an assumed threshold. The results from the inversion of geodetic data by Hashimoto and Jackson (1993) were used to speci-fy slip deficit rates for these faults. Each fault in this model is divided into nine equal-sized elements, three in the length direction and three in the width direc-tion, so that this model can simulate events as small as M6. The rate of stress accumulation is not necessarily constant for all faults, which may be attributed to the interaction between faults. It is interesting that fluctuations in the ampli-tude of stress changes with periods of about 2,000 years or longer are seen for some inland faults. Smaller events in which only one element on a fault ruptures frequently occur, but large events with three or more rupturing elements are rarely seen