Japanese researchers say the earthquake that struck off Indonesia's Sumatra Island last month generated disproportionately large tsunamis.
The waves caused by the magnitude-7.7 quake hit the Mentawai Islands, leaving at least 448 people dead.
A team led by Professor Kenji Satake of University of Tokyo's Earthquake Research Institute carried out an onsite survey earlier this month.
The survey found the waves that hit the island's coast reached as high as 5 meters, although many residents felt the quake itself was not so large.
The researchers concluded that the October 25th temblor was a "tsunami quake," a type that spawns disproportionately large waves.
They attribute the high death toll to the fact that many of the residents thought there would be no tsunami and didn't evacuate.
Professor Satake says the study shows that people in coastal areas need to flee to higher ground regardless of the intensity of a quake.