Following quake in Banda Aceh
Following quake in Banda Aceh Reuters

Three strong aftershocks have triggered a second tsunami warning for Indonesia after a massive earthquake struck off the coast of Indonesia at 6:38 pm local time Wednesday, measuring 8.9 on the Richter scale.

It occurred at a depth of 20.5 miles (33 km), about 300 miles (500 km) southwest of the city of Banda Aceh, located on the northern tip of Indonesia's Sumatra Island. A tsunami alert was issued immediately following the temblor.

The US Geological Survey (USGS) said the first 8.2-magnitude aftershock struck at 8:43 pm local time, 615 kilometers from Banda Aceh, just two hours after the earthquakeBut the Pacific Tsunami Warning Center issued fresh tsunami warnings for the entire Indian Ocean after three strong aftershocks struck the area within hours.

One after the other, the three aftershocks, including the first, measured 8.6, 8.2 and 8.1 on the Richter scale.

The sea level at the island of Simalu, meanwhile, has dropped by 10 meters, adding to fears that a tsunami is approaching.

Thailand has begun to evacuate people on the Andaman coast, a popular tourist destination, and from Krabi and Phang Nga Bay, on the popular resort Phuket Island.

The international airport has been closed in the Thai beach resort province of Phuket.

“All people along the Andaman coast must evacuate to safe areas. We expect a tsunami 1.6 to 2.0 meters high to hit Phuket and Phang Nga at 5:40 pm,” warned a scientist from the National Disaster Warning Center in an announcement on Thai television.

Malaysia also ordered a coastal evacuation. Sri Lanka has advised its residents on the eastern coast to evacuate as well, but has not made the recommendation an order.

German seismologists at the German Geo-Research Center (GFZ) who had helped install the warning system off the Indonesia coast following the deadly 2004 tsunami told the DPA news agency the first temblor had very little vertical movement, however.

The earthquake was the eighth most powerful quake recorded. Quakes in Indonesia in 2004 and 2005 are in third and tenth place on the list respectively. The list includes earthquakes as far back as 1900. Five of those on the list have been added since 2004.

Hundreds of thousands of people had died in the previous tsunami in the same area. However, large tsunamis are usually generated by earthquakes with vertical movement, scientists said, or landslides into the sea.