Enormous earthquake in Indonesia causes tidal waves (Updated)

26 December 2004

In the nine hours following the enormous earthquake off Sumatra, 14 earthquakes with magnitudes between 5.7 and 7.3 have occurred along the arc from Sumatra towards Nicobar and Andaman Islands.

The string of seismic events began when an enormous earthquake occurred off the West coast of Sumatra today at 11:59am ESST (0.58 UT). It measured magnitude 8.9 on the Richter scale.

The epicentre was approximately 320 km west of Medan, Sumatra. This earthquake is the result of plate collision, caused by the Australian plate moving northwards about 7cm per year.

"Shallow earthquakes of this size are very destructive and can cause serious damage in a radius of 200-300km," said Dr Cvetan Sinadinovski, Duty Seismologist with Geoscience Australia.

"A destructive tsunami has been generated in the Indian Ocean. A half a metre wave passed Cocos Island and caused abnormal tides and waves along the NW coast of Australia. It appears that the major threat for Australia has passed and damaging or destructive waves are considered unlikely," said Dr Sinadinovski.

Topic contact: media@ga.gov.au Last updated: October 4, 2013