Indonesia earthquake caused 5 fatal heart attacks

Indonesian authorities say five people had heart attacks and died after two large earthquakes triggered back-to-back tsunami warnings.

Indonesians grateful after twin quakes cause minimal damage

Residents surveying damage from two powerful earthquakes that awoke memories of the devastating 2004 Indian Ocean tsunami said Thursday they could hardly believe their luck.

Five people died from heart attacks in Indonesia's westernmost province of Aceh — closest to the epicentre of Wednesday's temblors — and several others were injured as they tried to flee to high ground.

But aside from a few cracks in the walls of houses and structural damage to one bridge, residents said it almost felt like nothing had happened.

"I really feel my prayers were answered," said Usman Basyah, 45, who lost one of his sons the 2004 disaster that killed 170,000 people in Aceh alone. "I'm so grateful."

Women cry on a street in Banda Aceh after a strong earthquake struck off Indonesia on Wednesday. (Junaidi Hanafiah/Reuters)

"We've gone through enough trauma already," he said as he handed change to customers at his small street stall.

Rahmi Novianti, a 25-year-old housewife who lives just outside the provincial capital, agreed.

"Yesterday, as I was running out of my house, I could see the tsunami coming in my mind, the entire village again being destroyed," she said. "That it didn't happen really feels like a blessing."

Indonesia, a sprawling archipelagic nation of 240 million people, straddles a series of fault lines that makes it one of the most seismically active places on the planet.

Aceh has experienced numerous "mega thrust" quakes over time.

It's these temblors that cause the seabed to rise or drop vertically, sometimes by five or 10 metres, displacing massive amounts of water that race across the ocean at jetliner speeds.

But experts say Wednesday's 8.6-magnitude quake and the 8.2-magnitude aftershock occurred on what is known as a "strike-slip" fault. The sea floor shifted horizontally, creating more of a vibration in the water.

As result, the only wave generated was less than 80 centimetres high.

Though the shaking on land was fierce, lasting nearly four minutes and triggering mass panic, only five people died, Asmadi Syam, head of Aceh's disaster management agency, told MetroTV. "All from heart attacks," he added.

At least four other people were injured.

The power of the quakes triggered a tsunami watch in countries all along the Indian Ocean, from Australia and Pakistan all the way to Africa.

Recalling the 2004 disaster that killed 230,000 people in nearly a dozen nations, sirens sounded along coastlines and warnings spread like wildfire by mobile phone text messaging.

Evacuations began immediately.