Very large earthquake off Sumatra has potential for tsunami

29 March 2005

A very large earthquake with a magnitude of 8.5 occurred off the coast of northern Sumatra at 2:09am on Tuesday 29 March (Australian Eastern Standard Savings Time).

The epicentre is located approximately 205 km west north-west of Sibolga, Sumatra, Indonesia, and 245 km southwest of Medan, Sumatra. This is south-east of the Boxing Day earthquake, and there have been six after-shocks in the two hours following the earthquake.

"Shallow earthquakes of this size are very destructive and can cause serious damage within 200-300km of the earthquake," said Dr Phil Cummins, Duty Seismologist with Geoscience Australia.

"The Bureau of Meteorology has reported a ten centimetre tsunami was measured by the tide gauge at Cocos Island. Any tsunami observed in Western Australia is unlikely to be larger than that observed in Australia on Boxing Day. It will arrive at North West Cape (near Exmouth) at 4am WA local time and take two to three hours to go up and down the coast."

"There is potential for a tsunami to affect other regions in the Indian Ocean."

This earthquake is the result of plate collision, caused by the Australian plate moving northwards about 7cm per year.

For a list of the most recent earthquakes or to report a felt event visit the Geoscience Australia website -

Topic contact: Last updated: October 4, 2013