BENGKULU, Indonesia, Sep 13 (Reuters) Indonesia's Sumatra island was pounded by aftershocks today after a massive earthquake killed at least eight people and buried many others under collapsed buildings.
Tsunami warnings were repeatedly issued and lifted for Indian Ocean countries after the magnitude 8.4 earthquake -- the biggest anywhere in the world this year -- was followed over the next 18 hours by 22 tremors ranging in intensity from 4.9 to 7.8.
An Australian seismologist said the region was lucky to have escaped a devasting tsunami similar to the one triggered by the 2004 quake that killed more than 280,000 people.
''There was a tsunami created by the earthquake, it just travelled in a southwest direction away from land,'' said Mike Turnbull at Central Queensland University.
The initial quake, which happened on the eve of the Muslim fasting month of Ramadan, was felt across the Malaysian peninsula and Indonesian archepelago, cutting communication lines and sparking fears that the region would awake on Thursday to scenes of widespread devastation.
There was panic and chaos in the hours that followed and as the aftershocks continued, but by Thursday afternoon it appeared the region may have been spared a major disaster.
A Reuters photographer in Bengkulu, a coastal city of about 300,000 people and the closest major town to the epicentre of the quake, said the situation there appeared calm, with shops re-opening and people milling around.
Many people chose to sleep out in the open yesterday night rather than return indoors, said a Red Cross official in Bengkulu, a mountainous area that attracts few foreign tourists.
''My family and neighbours are evacuating to higher ground.
Everyone in the place where I live decided to evacuate,'' said 35-year-old Padang resident Eri Kamra.
Walls of buildings in the city had cracked, but most homes were still standing -- although a school was badly damaged and the ceiling of the main hospital had also come down.
The mayor of Padang, the capital of West Sumatra, said many people were trapped under collapsed buildings.
MANY TRAPPED A Reuters witness there said a four-storey car showroom had collapsed, trapping several staff. At least one body was carried away from the rubble.
''Many are still trapped underneath the rubble from last night's quake,'' Padang Mayor Fauzi Bahar told Reuters.
Part of Padang's main hospital also collapsed, and some injured people had to be moved out of wards to the relative safety of tents.
Rustam Pakaya, head of the Indonesian health ministry's crisis centre in Jakarta, said latest casualty figures showed eight people had been killed and 49 injured.
''The North Bengkulu area has been identified as the worst hit with half the area destroyed,'' he said.
The area, with an economy relying heavily on coffee and rubber, was hit seven years ago by a powerful earthquake that killed more than 100 and damaged thousands of buildings.
Indonesia suffers frequent quakes, as it lies on an active seismic belt on the so-called Pacific ''Ring of Fire''.
''There is no explanation about why there are so many quakes hitting Indonesia at this time but Indonesia is perhaps the most active earthquake area in the world,'' said geophysicist Dale Grant of the US Geological Survey.
''We can expect aftershocks to continue for some time.'' A huge earthquake measuring more than 9 struck the same area of Indonesia on December 26, 2004, causing a massive tsunami and more than 280,000 deaths in countries across the Indian Ocean region.
Australian seismologist Turnbull said the way the seabed ruptured caused that tsunami to head towards Sumatra, but Wednesday's quake saw a tsunami travel southwest, away from land, where it eventually petered out in the southern oceans.
''In this case the plate bodies that cause the earthquake ruptured in a way that saw the water thrown forward to move away from Sumatra. It was totally different to the Boxing Day 2004 mechanism,'' said Turnbull.
A team of ministers arrived in Bengkulu, along with a medical team, a tonne of medications, baby formula, tents and body bags.
The ministers were due to fly back to Jakarta late afternoon to brief President Susilo Bambang Yudhoyono on the situation.
REUTERS JT BST1334