Photos courtesy Tonga Ministry of Lands, Survey and Natural Resources

Following the strongest earthquake ever recorded in Tonga major structural damage to the Queen Salote Wharf no. 2 and 3, in Nuku'alofa, and to the Niu'ui Hospital and other structures in Ha'apai is being assessed by Tonga's Ministry of Lands.

In the Ha'apai group, which was close to the epicentre of the violent earthquakes on May 4, many buildings were cracked including the largest, the Lopeti Vi building in Pangai, and long running cracks have appeared in the roads and concrete paving, while churches throughout the group including the FWC at Pangai have reported structural damage.

"Cracks were seen at the main wharf at Ha'apai, the walls of the main hospital, church buildings, brick dwelling houses and structures both at the main island and Ha'ano island," Tonga's National Emergency Management Office reported, while the small outer islands of Ha'apai remained to be contacted.

The office reported that according to the Pacific Tsunami Warning Center in Hawaii the earthquake epicentre was roughly 20 kilometres east of Pangai. "The magnitude was recorded as: 7.8 at the Richer Scale by PTWC and 8.1 on Tonga seismic...… thus, this was the strongest earthquake ever recorded in Tonga."

The earthquake later downgraded to a magnitude 7.9 was also the world's biggest in more than a year.

A team from the Ministry of Works, and Lands, including architect Leveni 'Aho left for Ha'apai on May 5 to assess the damage.

Ring of fire

The Minister of Lands, Survey and Natural Resources, Hon. Fielakepa, said today he believed the epicentre of the quake was actually in the vicinity of the volcanic Kao and Tofua islands in Ha'apai.

He said that a Ministry of Works report showed the epicentre in this area west of Ha'apai, "This is the area where islands frequently are formed."

Information was received from the Surveyor General Tevita Malolo, and the Principal Government Geologist Kelepi Mafi who were located on the islands of 'O'ua and Lifuka at the time of the seismic event. They were part of a regional workshop on energy held in Ha'apai and most of the delegates were overnighting on 'O'ua, he said.

Fielakepa, a former Governor of Ha'apai, had been with the group looking at the diesel generated power supply in Ha'apai and had left Uiha only hours before the earthquake.

He said the delegates from Vanuatu, Canada, Fiji, Solomon Islands, Samoa, Rotuma, Tonga and SOPAC and other island representatives were all well - "but they said, Fielakepa how did you know there was going to be this seismic event for us!"

"I am always concerned with the possibility of major seismic events in Ha'apai because they are right on the Ring of Fire, and there is often activity around Tofua and Kao."

Seismic stations

The Ministry of Lands has seismic stations in Vava'u (Mo'unga Talau), Ha'apai (Hihifo) and Tongatapu (Nukuhetulu), and two others in the Niuas that were installed with Japanese aid. The information was collected at the hub station in Vaololoa by satellite (VSAT) transmission from the outer island stations.

Fielakepa was in his Nuku'alofa office when the earthquake struck, "I went straight to Vaololoa to check the data and our geologist Rennie Vaimo'unga was already there. We can't tell if there will be a tsunami from the data, but we get an idea of the strength of the earthquake and it showed 5.5 at Vaololoa."

"Rennie reported that the reason for the difference between the US Geological Service and our local network result is due to the limited number seismic stations that record the earthquake. To locate an event, it needs a minimum of three seismic stations. The more seismic stations recording an event the result obtained will be more accurate."

The seismic stations in the Niuas were not operating during the quake, said Fielakepa, and they will have to be inspected and restored in order to get more accurate results.