Poster of the Northwest Sumatra, Indonesia Earthquake of 02 November 2002 - Magnitude 7.4
The earthquake occurred as a result of thrust-faulting on the boundary between the subducting Australian plate and the overriding Sunda block of the Eurasian plate. In the region of the epicenter, the Australian plate is moving about 6 cm/year in a northerly direction against the Eurasian plate. The direction of relative plate motion is oblique to the northwest trend of the plate boundary. Earthquakes such as that of November 2 accommodate the component of plate-motion that is perpendicular to the trend of the plate boundary. The component of plate-motion that is parallel to the trend of the plate boundary is mostly accommodated by strike-slip faulting in the interior of the island of Sumatra. The largest thrust-fault earthquakes in the Sumatran subduction zone in the last two centuries were that of 1833, which had a magnitude of 8.8-9.2, and that of 1861, which had a magnitude of 8.3-8.5.
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