A powerful earthquake has struck an hour ago, at 8.30UT, very close to the place where a similar event occurred on December 26th 2004. The earthquake has an estimated magnitude of 8.7 and occurred at a depth of 33km, according to NOAA. The map below shows the location of the event and the potentially affected areas.
Note that the wave is expected to arrive to Sumatra right now, at the time of writing this. It is not granted that an earthquake, even a powerful one such as the present one, will generate a train of tsunami waves; however it is quite likely that this is what is occurring. The extent of the potential destruction cannot be estimated, but it is advisable to move to higher areas if you find yourself in the coastal region of Sumatra or anywhere on the coasts of Indian ocean.
The December 26th 2004 tsunami hit very hard the region, with over 230,000 casualties according to wikipedia. More recently, another powerful earthquake off the coast of Japan also created massive destruction. I sincerely hope it is not happening again...
UPDATE: It appears that the danger of a catastrophe similar to that of 2004 is over. However, a watch is in progress through much of the Indian Ocean, in 28 countries; people have been asked by authorities to move away from coasts in an extended area. The Andamans and Nicobars islands have been put on special alert.
The magnitude of the earthquake has been now assessed at 8.6 of the Richter scale; an aftershock of magnitude 6.5 has later been registered.
You can follow the events live on NDTV here.
UPDATE: Good news ! It now appears that the earthquake has generated no big waves in the area. The alert is still on, but no anomalous waves have been observed in any of the regions around the earthquake epicenter.
Tsunami Expected In Sumatra Now