The 2004 earthquake was an interplate earthquake
between the Indo-Australian plate and the Andaman
(or Burma) microplate, a part of the Eurasian plate
(Figure 1). The Indo-Australian plate subducts along the
Sunda Trench at a rate of approximately 5 cm per year,
and the direction of subduction changes from normal to
the trench to oblique toward north. This subduction
causes upper plate to be dragged and deformed up to a certain limit, then suddenly rebound to cause an interplate earthquake.