5.1 General Tectonic Environment
The island of Sumatra sits on the Southeast Asian plate, which over rides the subducting Indian
and Australian oceanic plates that converges obliquely at about 50 to 70mm/yr [Prawirodirdjo et
al., 2000]. The oblique convergence is partitioned into two components: the dip slip is
accommodated on the subduction interface, and the strike-slip component is accommodated
largely by the Sumatran Fault [McCaffrey, 1992; Sieh and Natawidjaja, 2000].
The 1900km long Sumatran Fault Zone (SFZ) traverses the back-bone of Sumatra, within or
near the active volcanic arc. [Sieh and Natawidjaja, 2000]. At its northern terminus, the Great
Sumatran Fault Zone transforms into the spreading centers of the Andaman Sea [Curray and
others, 1979]. At its southern end, around the Sunda Strait, the fault curves southward toward
and possibly intersects the Sunda trench [Le Pichon et al., 1981; Diament et al., 1992; Sieh and
Natawidjaja, 2000]. See Figure 5.1 – Plate tectonic Environment of Sumatera Island for detail
information.