We investigated the changes in slip rate and recurrence interval of repeating earthquakes using 3-D numerical simulations of a subduction zone involving large and small asperities and based on a rate- and state-dependent friction law. Our results reveal that the postseismic slip of a large earthquake can trigger an event at a nearby small asperity, although the event may differ to other repeating earthquakes at the asperity because the slip velocity of the event tends to be slower than that of other repeaters; the slip distribution also differs. These results probably explain the observation that the slip amount estimated from repeating earthquake analyses tends to be smaller than that estimated from GPS analyses for large amounts of postseismic slip, as observed for postseismic activity following the 2003 Tokachi-oki earthquake.