The recent major earthquakes that have occurred in Chile (February 2010), New Zealand - Canterbury (September 2010), New Zealand - Christchurch (June 2011) and Tohoku (March 2011) have raised questions such as: Do earthquakes of major intensity cluster around the world? Have there been other, previous series of major earthquakes around the world? Are other major earthquakes more likely to occur in the very near future, if so where? These are all very challenging questions. This EQECAT briefing (part one of three) begins to answer some of them.

Rather worryingly, the conclusion is that if the current earthquake cycle of giant earthquakes , which started in 2004 with the Christmas Eve Sumatra event, follows the one that occurred between 1950 and 1965, then one may expect that the cycle is only half complete. 

Hampden comment: an excellent short and generally understandable report on seismicity with some good tables and charts for enthusiasts.