HONG KONG (Reuters) — A mega-tsunami rivaling the deadly one in 2004 struck southeast Asia more than 600 years ago, two teams of geologists said after finding sedimentary evidence in coastal marshes.
“Tsunamis are something we never experienced before, and after 2004 people thought it was something we would never experience again,” Kruawun Jankaew of Chulalongkorn University in Thailand said in a telephone interview.
“But from this, we are able to identify that the place has been hit by a mega-tsunami in the past,” she said. “So even though it is infrequent for this part of the world, it still happens and there is a need to promote tsunami education for coastal peoples.”
The tsunami in 2004 left 230,000 people either dead or missing across Asia, from Sri Lanka and India to Thailand, the Maldives and Indonesia. More than 170,000 victims were in Aceh Province in Indonesia.
Ms. Jankaew’s team studied a grassy plain on Phra Thong, an island north of Phuket in Thailand, where the 2004 tsunami reached wave heights of 65 feet above sea level.
A separate team led by Katrin Monecke from the University of Pittsburgh looked at sedimentary records on coastal marshes in Aceh, where the waves reached 115 feet.
They explored low areas between beach ridges called swales, which are known to trap tsunami sand between layers of peat and other organic matter, and discovered a layer of sand beneath the most recent layer, from 2004, that was from an event that occurred 600 to 700 years ago.
Scientists are trying to determine the scale of the tsunami that happened long ago. “We will look at the thickness and grain size of the sediment and we can calculate how fast the tsunami was, how far inland it went and the floor depth,” Ms. Jankaew said.
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