M7.8 - NORTHERN SUMATRA, INDONESIA

Tectonic Summary

RELATIVE PLATE MOTIONS
The broad red vectors represents the motion of the Australia Plate relative to the Sunda Plate in the region. The motion of the Australia Plate is generally 50-66 mm/yr northward with respect to the Sunda Plate in the southern region, but diminishes to 40-50 mm/yr towards the north.

The Banyak Islands, Sumatra earthquake of April 6, 2010 occurred as a result of thrust faulting on or near the subduction interface plate boundary between the Australia-India and Sunda plates. At the location of this earthquake, the Australia and India Plates move north-northeast with respect to the Sunda plate at a velocity of approximately 60-65 mm/yr. On the basis of the currently available fault mechanism information and earthquake depth, it is likely that this earthquake occurred along the plate interface.

The subduction zone surrounding the immediate region of this event last slipped during the Mw 8.6 earthquake of March 2005, and today's event appears to have occurred within the rupture zone of that earthquake. Today's earthquake is the latest in a sequence of large ruptures along the Sunda megathrust, including two M 7.4 earthquakes beneath Simeulue 125 km to the north in 2002 and 2008; a M 9.1 earthquake that ruptured to within 125 km north of this earthquake in 2004; a M 8.5 375 km to the south in 2007; and a M 7.5 260 km to the south near Padang in 2009.

Seismic Hazard Poster of Western Indonesia: JPG | PDF

Earthquake Information for Asia

Earthquake Information for Indonesia