Warning System Put to Test by Recent Tsunami Threat
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.
Tsunami siren
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 on January 15th. When the January 15th tsunami hit, it took half an hour 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.