Researchers say that earthquakes which would pose no threat today could lead to cities being swamped by water as the sea level rises.
The researchers focused on the city of Macau in China, which is currently considered safe from tsunamis, despite lying in an earthquake zone.
But a three-foot rise in sea level would increase the risk of tsunamis inundating the city by up to 4.7 times, the researchers found.
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Such a rise is predicted to occur in the area by 2060.
Lead researcher Dr Robert Weiss of the Virginia Polytechnic Institute and State University said, ‘Our research shows that sea-level rise can significantly increase the tsunami hazard, which means that smaller tsunamis in the future can have the same adverse impacts as big tsunamis would today.
‘The South China Sea is an excellent starting point for such a study because it is an ocean with rapid sea-level rise and also the location of many mega cities with significant worldwide consequences if impacted.’