Tonga was hit by a huge jolt recently. RNZ Pacific finds out how well the tsunami warning system did in alerting Tongans to imminent danger.
Tongans were given a rude awakening just before midnight on Friday 11 November, with a 7.3 magnitude earthquake shaking the islands across the Kingdom.
Seventy-five tsunami sirens immediately rang out on coastal areas of the Tongatapu, Ha'apai, 'Eua and Vava'u, alerting residents to a tsunami threat.
"In Tongatapu, only those at the coastal areas evacuated to the evacuation points located inland...until the tsunami warning was cancelled at almost 4 o'clock in the morning," disaster response officer on Vava'u Mafi Penisoni said.
"The MET department recorded only 1.5 metre waves, but it didn't affect any of the coastal areas and there's no report of any damage," Penisoni added.
RNZ Pacific's correspondent in Tonga, Iliesa Tora, said he was drinking kava with friends at the time of the quake. After hearing the sirens, he drove off towards a high area in the interior of Tongatapu.
"We heard the shake and it went for some time, longer than a minute...and then we heard the sirens," Tora said.
"It was packed all along the road between town and Mata-ki-'Eua...we waited and just kept listening to Radio Tonga for updates, and when they said it was safe, we returned home."
The sound of the sirens surprised many on Tongatapu as the early warning system had long been the centre of ridicule in Tonga, after successive failures to sound-off in time.
When the Hunga Tonga-Hunga Ha'apai volcano erupted on 15 January, for example, the sirens did not sound-off until more than half an hour after the tsunami waves struck.
"On Friday night, it really worked well," Tora said.
"It was a big improvement from what happened January 15th. When the January 15th tsunami hit, it took half an hour a later before we could hear the siren and it was very weak. This one, the whole of Tongatapu could hear the siren," he said.
Earthquakes are common in Tonga. According to the United States Geological Survey, Tonga, Fiji and Indonesia experience the most earthquakes per unit area. The Kingdom experiences an average of three magnitude 6 plus earthquakes a year, although few trigger tsunami alerts.
In 2009, an 8.1 magnitude earthquake generated a tsunami that killed nine people on Tonga's northern-most island of Niuatoputapu, and 149 in neighbouring Samoa.
The incident prompted authorities to boost the country's civil defence infrastructure, and with the help of foreign donors, 75 tsunami warning sirens were installed in the country. An evacuation system was developed, with regular drills organised for schools and government offices in collaboration with radio and TV stations.
The self-evacuation procedure played a crucial role when the Hunga Tonga-Hunga Ha'apai volcano erupted on 15 January. Tens of thousands of Tongans abandoned their homes for higher ground, leaving entire villages and neighbourhoods empty before the tsunami waves struck.
Tongatapu reported only one fatality, Angela Glover, a British expat who ran a dog shelter and died trying to rescue her canines. A total of three people died in the Hunga Tonga-Hunga Ha'apai volcanic eruption.
Meanwhile, Niue Broadcasting reports that the sirens were not operating there.
Shortly after the tremor, a tsunami warning was issued for Niue prompting coastal residents to evacuate to higher ground.
But those who had social media received the warning on the government's social media platform promptly and took actionm the broadcaster reports.
Radio Sunshine also provided regular updates. Niue Broadcasting said the only siren that sounded was from the National Disaster Management Office vehicle.