A tsunami warning is unlikely to result in problems for Otago's residents but marine users need to be cautious in coastal waters this morning, Dunedin's civil defence authority says.
Waves of 20cm-30cm were expected to reach Otago's coastline about 2am today, and the after-effects of Chile's 8.3-magnitude earthquake could be felt until early this afternoon, Dunedin City Council civil defence manager Neil Brown said.
The waves, which were expected to reach 30cm north of Otago Peninsula and 20cm south of it, were due to reach the coastline during low tide and presented little danger to those on land, he said.
However, those using the waters around the coast and in river mouths this morning should be cautious of increased tidal flows and currents.
''If people are doing whitebaiting or other shore-based activities in the morning they should be cautious about what they are doing.
''These disturbances can go on for some hours. There could be unusual sea patterns for up to 12 hours,'' Mr Brown said.
Any risk of increased tidal action should pass by 2pm, he said.
Senior Sergeant Brian Benn said Southern police had advised whitebaiters camped on riverbanks in Southland and Otago of the tsunami warning.
Years 3 and 4 Lumsden School pupils who were to have stayed overnight in Pounawea on a school camp also had their trip cut short because of the tsunami threat.
Principal Andrew Watson said the 24 children left Pounawea for home about 7.15pm yesterday as a precaution, after Otago's coastline was included in the warning.
''As soon as we heard that the warning had been extended along the New Zealand coastline it was a no-brainer,'' he said.
Waves of up to 3m were recorded in some locations as the earthquake reverberated through the Pacific Ocean.
Mr Brown said even that worst-case scenario would present a risk to life in Dunedin.
''Three metres is less than our maximum credible event,'' he said.
''People shouldn't feel alarmed, just be cautious.''
The Ministry of Civil Defence & Emergency Management issued a tsunami warning for New Zealand's east coast about noon yesterday after the quake rocked Chile's capital Santiago about 11am (New Zealand time), killing at least five people and causing the evacuation of more than a million.
Waves of up to 1m could be expected on some areas of New Zealand's east coast and the ministry warned of unusually strong tidal currents in Coromandel, the East Cape and Gisborne, and Banks Peninsula.
Beachgoers were warned to expect unusually strong currents and unpredictable water flows near the shore and to stay out of waterways, including rivers and estuaries.
''Historically, the first waves have not been the largest, and the same may be true for this event,'' the ministry said.
University of Otago senior lecturer in geography Dr Wayne Stephenson said the reason areas such as Banks Peninsula were more at risk of tsunami, while Dunedin less than 300km away was at less risk, was because of the profile of the sea floor.
''Changes in depth alter how the wave refracts as it moves across the ocean,'' he said.
''The shelf off the east coast is rather variable and so the wave is focused towards particular parts of the coast, such as Banks Peninsula.
''In terms of the risk to Dunedin, people should follow Civil Defence warnings and avoid the shoreline while the tsunami warning is in effect.
''Even though the Otago coast is not mentioned in the Civil Defence warnings, I would still advise caution.''
