Besides the studies of past earthquakes in particular
regions, seismologists have attempted to make global
assessments of probable maximum earthquake size. Because
of infrequent nature of such giant earthquakes,
global collection of data is needed to increase our
sample and knowledge on such large earthquakes. A
comparative studies of subduction zones showed
that there are two end members of subduction zones,
i.e., Chilean type and Mariana type, among which only the
former types can produce great earthquakes. Subsequent
studies proposed that the age of subducting plate and
plate convergence rate may control the maximum size of
earthquakes; larger earthquakes occur in subduction
zones where younger plate subducts at a higher convergence
rate. However, re-examination of the relation
among the plate age, convergence rate and the maximum
earthquake size, made after the 2004 earthquake, showed
that such a relationship is not as strong as it was believed
before.