Tsunamis

Tonga lies along a subduction fault line between two tectonic plates, which causes frequent earthquakes and undersea landslides with the potential to generate tsunamis. Historically, around 20 tsunamis have affected a large number of islands in Tonga with the majority of them being small (<1 m) with little recorded damage.

On 15 January 2022 Tonga's Hunga Volcano erupted in a sudden and explosive way causing a large local tsunami that devastated villages and resorts along the western shore of Tongatapu and in the Ha'apai island group as well as a far-field tsunami that caused damage and deaths thousands of kilometers away. According to an estimate,  84,176 people (84 per cent of the population) on Tongatapu, Ha’apai and ‘Eua) were affected, particularly by ashfall. Around 3,000 people were displaced in the immediate aftermath, including some evacuated from seriously affected islands off the coast of Tongatapu and in the Ha’apai island group.

The 2011 Japan earthquake (9.0 magnitude) generated 17.8 cm wave heights in the Tonga region. In 2009 an offshore 8.1 magnitude earthquake generated a tsunami that struct Tonga, killing nine people, and destroying around half of the houses on the island of Niuatoputapu. The greatest single risk to the country would be an earthquake with magnitude more than 8.8 in the Tonga Trench, 100 km east of Tonga.