The risk of a large earthquake in the Indian Ocean was “significantly underestimated” at the time of the Boxing Day tsunami a decade ago, an expert has said.

Tim Henstock, senior lecturer in ocean and earth science at the University of Southampton, said only a “small number” of people were involved in monitoring seismic activity in the region when the massive 9.1 magnitude earthquake struck, causing the earth to physically wobble on its axis.

The earthquake – 23,000 times more powerful than Hiroshima – caused shifts in the ocean floor which displaced enough water to fill a tank 1.6 kilometres wide, 1.6 kilometres high and more than 11 kilometres long.

Looking at Thailand, Sri Lanka and the coast of India, an early warning system would have made quite a significant difference

Henstock said: “In 2004, in the Indian Ocean there really wasn’t any system in place. There were a small number of people working on hazards in that subduction zone (when one of earth’s tectonic plates sinks underneath another after they collide).

“The risk of a big earthquake was significantly underestimated at that point in time. Whereas the risk in the Pacific was well known, there was essentially nothing in the Indian Ocean.”

Henstock said the lack of an early tsunami warning system was a “significant factor” in the devastation caused.

“Looking at Thailand, Sri Lanka and the coast of India, an early warning system would have made quite a significant difference, where there was a couple of hours of travelling time,” he said.

“The lack of an early warning system meant people in Sri Lanka and elsewhere would not have been aware of the earthquake happening.

“The complicating factor was the Sumatra mainland was so close to the subduction zone. The tsunami at Banda Aceh arrived about 20 minutes after the earthquake happened.

“That’s a scenario which is very difficult for early warning systems to cope with.”

Henstock said deep water pressure sensors in the Indian Ocean were now used to detect a tsunami so warnings could be issued to any areas expected to be hit. But he said there were still “potential problems” when a tsunami only had a short distance to travel to reach coastal areas.

Henstock said that while a similar-sized earthquake in the same region would only be expected in “several hundred years ... if it was repeated right now, there would certainly be a much higher chance of warning people in India, Sri Lanka and Indonesia”.

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