A big earthquake can trigger a lot of other earthquakes right around the world.
This is most likely due to water flow, since large underground bodies of water react to the very low frequency seismic waves. Mostly this is observed as well-water changes, but you can imagine what this does to fault systems!
This reinforces my ideas that water is the main driver behind 'interior' earthquakes. Other people haven't come around to this yet, so I'm waiting... :)