Tsunami sparks tide alert

19:10, Feb 06 2013

Marlborough boaties have been warned to look out for unusual tidal movements over the next day, following a tsunami warning caused by a massive earthquake off the Solomon Islands.

The magnitude 8.0 earthquake east of the Solomon Islands yesterday afternoon sent two 1.5-metre waves toward the western side of Santa Cruz Island, damaging around 50 homes and properties.

An updated potential tsunami threat advisory was issued last night for the west coast of New Zealand between Taranaki and Milford Sound and the threat was likely to be low.

Any tsunami was "likely to be undetectable except in enclosed bays that traditionally have abnormal current flows", the Ministry of Civil Defence and Emergency Management said.

Maritime officer Dave Baker said yesterday shallow areas of the Sounds and places such as Port Underwood could be affected, although any surge was only expected to be about 80cm by the time it reached Marlborough.

The affects were more likely to be "unusual tidal movements" affecting berthed ships and boats or moored vessels rather than any wave effects at Tory Channel, he said.


Marlborough marine farmers have been affected by surges in the past. In March 2011, tsunami currents caused by the massive earthquake in Japan snapped anchor ropes on marine farms in the Marlborough Sounds, tangled mussel lines and damaged mussels ready for harvest, but tidal surges expected following a 7.6 magnitude earthquake near the Kermadec Islands in July that year did not eventuate.

Yesterday, a navigational warning was issued for boaties on VHF marine radio and through the Port of Marlborough channel in Picton to ensure people were aware of the possible water movements.

A "warning" by the Pacific Tsunami Warning Centre was cancelled just before 5pm, although New Zealand authorities were still urging care.

The Ministry of Civil Defence and Emergency Management issued a national advisory for tsunami potential marine and beach threat. Marlborough and Nelson-Tasman were included in the alert, along with Gisborne, Bay of Plenty, Auckland, North Cape, Waikato, Taranaki, Manawatu-Wanganui, Kapiti, West Coast, Milford, Dunedin and Chatham Islands. Kaikoura and the Wellington-Wairarapa coasts were not included in the alert.

Marlborough District Council emergency service co-ordinator Mark Wheeler said Marlborough was generally sheltered by the North Island from Pacific tsunami but the council was monitoring the situation.

A ministry spokesman said historical comparisons suggested any waves were likely to be greatest in the central west coast of New Zealand, between Hokitika and New Plymouth.

The first waves were expected to be small and to hit North Cape shortly after 6pm, travelling south and hitting Westport about 8.30pm. The largest waves would hit between two and eight hours later.

In many areas the main concern was likely to come from strong harbour currents and surges in river mouths.

In April 2007, more than 50 people were killed and thousands lost their homes when a magnitude 8.1 quake hit the western Solomon Islands, sending waves crashing into coastal villages.


The Marlborough Express