Large Aceh quake triggers Indian Ocean tsunami warning

An earthquake with an magnitude of 8.7 has struck under the sea off Indonesia's northern Aceh province.

The quake triggered a tsunami warning across the Indian Ocean region.

The Pacific Tsunami Warning Center (PTWC) said it was not yet known whether a tsunami had been generated, but advised authorities to "take appropriate action".

The region is regularly hit by earthquakes. The Indian Ocean tsunami of 2004 killed 170,000 people in Aceh.

The US Geological Survey (USGS), which documents quakes worldwide, said the Aceh quake was centred 33km (20 miles) under the sea about 495km from Banda Aceh, the provincial capital.

It was initially reported as 8.9 magnitude but was later revised down to 8.7 by the USGS. Strong aftershocks were also reported.

The PTWC warning said quakes of such a magnitude "have the potential to generate a widespread destructive tsunami that can affect coastlines across the entire Indian Ocean basin".

But Bruce Presgrave of the USGS later told the BBC that the nature of this quake made it less likely a tsunami would be generated, as the earth had moved horizontally, rather than vertically, therefore had not displaced large volumes of water.

"We can't rule out the possibility, but horizontal motion is less likely to produce a destructive tsunami," he said.

Sutopo, a spokesman for Indonesia's disaster mitigation agency, said the quake had been felt "very strongly".

"Electricity is down, there's traffic jams to access higher ground. Sirens and Koran recitals from mosques are everywhere," he told Reuters.

The tremor was felt as far away as Singapore, Thailand and India.

The Thai office of disaster management said people along the coasts of Phuket, Phang Na and Andaman province should heed warnings and evacuate.
Map showing the location of the earthquake

Tsunami warning sirens, set up in many vulnerable areas after the 2004 disaster, were heard in Phuket, where correspondents said people were calmly following evacution routes to safe zones.

Reuters quoted Indonesian officials as saying there had been no immediate reports of damage of rising water levels in Aceh.

Indonesia straddles the Pacific Ring of Fire, a zone of major seismic activity.

The BBC's Karishma Vaswani in the Indonesian capital, Jakarta, says there were reports of the ground shaking for up to five minutes. Contact with people in the immediate area around the quake has not been possible so far, says our correspondent.