explainer

Why there was no warning for the tsunami that devastated Indonesia.

– With AAP

Experts are piecing together how a deadly tsunami could strike Indonesia without warning on Saturday night.

At least 281 people have been killed after the crashing waves hit coastal areas along western Java and southern Sumatra islands, with more than 1,000 others injured and dozens still missing.

Experts now say the Sunda Strait tsunami was caused by a major eruption from the Anak Krakatau volcano, also known as the “Child of Krakatoa”, on Friday, but are still pinpointing exactly how.

Oceanographer Dr Simon Boxall told Associated Press the tsunami was made worse by a high tide, and caused by either lava flows after the eruption or, more likely, underwater landslides as a result of the eruption.

Why was there no warning for residents?

“The problem is it occurred during a high tide, a high spring tide, which means that the water levels were already very, very high,” Dr Simon Boxall said.

“It would have only taken about 10 minutes for the tsunami to hit the coast to the west, took about an hour to hit the east.”

Dr Boxall told AP that even if there were enough time to get a warning out to coastal residents, there were no buoys in that area to detect early signs.

However, he cautioned those who are now asking “well, why aren’t there buoys there?” to consider the facts.

“It would take thousands of detector buoys, which are difficult to maintain (and are) expensive,” he explained.

“Cost isn’t the only issue. It’s also a question of networking them to actually successfully detect a tsunami.”

Dr Boxall said that because unlike many other tsunamis caused by earthquakes, there was nothing that immediately triggered fear in people that a tsunami could be coming.

“And so there wasn’t even the chance for people to realise an earthquake would lead to a tsunami [because there was no earthquake].”

He concluded that because of the speed the waves moved “there was very little that could have been done”.

“And it is just a tragic fact of nature.”

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The abruptness of the disaster was apparent in a chilling video captured on Saturday night.

A band called Seventeen performing at a resort in Banten province for power company PLN’s end of year celebrations was on stage when the tsunami struck.

The performers were among the hundreds of terrified people swept into the sea.

Tragically, two of the band’s members, along with their manager, were later found dead. The drummer, a crew member and the lead vocalist’s wife are all still missing.

The death toll, currently at 281, is feared to increase as at least 57 people remain missing.

It was the second deadly tsunami to hit Indonesia this year, but the one that killed more than 2500 people on the island of Sulawesi on September 28 was accompanied by a powerful earthquake that gave residents a brief warning before the waves struck.

In the city of Bandar Lampung on Sumatra, hundreds of residents took refuge at the governor’s office, while at the popular resort area of Anyer beach on Java, some survivors wandered in the debris.

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