Editorial: Tsunami alert better but not perfect

Police ask a man to move to safety at Mission Bay in Auckland. Photo / Natalie Slade

Civil Defence has done better this time. On Sunday morning, the organisation did not seem asleep on the job, as it did on the morning of the Samoan earthquake last year.

This time, the organisation could have been quicker to issue a tsunami alert on Saturday night. An hour after Chile was shaken by the magnitude 8.8 earthquake, Civil Defence was discounting the risk of tidal waves, but by midnight it was warning otherwise.

Most people would have received the warnings by radio on Sunday morning, when it was brilliantly sunny over most of the country and many would have been heading for a beach.

It is to the credit of Civil Defence's communications effort, and the radio stations that gave their morning programming over to the tsunami warning, that most people did the sensible thing. Scheduled coastal events were cancelled for the day and most intending beachgoers found something else to do.

Most, but not all. There is no accounting for the few who feel the urge to defy the risk of sudden tidal surges, and unless they are children there is no need to protect them from themselves.

Police and lifeguards do not need the powers some are suggesting they should have in emergencies. The responsibility of the authorities is to see that people are properly informed and warned of the dangers. If adults want to walk through a safety cordon, it is their choice.

The few who did so on Sunday came to no harm. The ripples from the Chilean quake were barely perceptible on the New Zealand coast, like those from the Samoan shake.

If this happens too often, the warnings will cease to be taken seriously. It is a worry that oceanographers at the Pacific Tsunami Warning Centre in Hawaii yesterday admitted they erred on the safe side. Ocean monitoring could surely be more accurate and reliable.

From sensors in the sea we learn the magnitude of a wave and the projected direction and distance it will travel. These are low and long volumes of water and their modest height is no indication of their destructive potential. Doubtless their coastal impact, or lack of it, depends partly on the contours of the seabed and shore that they strike, but surely more could be predicted from mid-ocean.

Why, for example, did the Chilean tsunami arrive with more force on the coast of Japan, twice as far from the epicentre as New Zealand? Plainly nowhere around the vast Pacific is immune to the wash from offshore earthquakes on its fiery perimeter.

The waves from this one took more than 12 hours to reach us, ample time for Civil Defence to prepare. The real test will be when a shallow undersea quake happens much closer. If the tremors are felt here it will be too close for any warning.

A tsunami could arrive within minutes, just as it did on the southeast coast of Samoa. The safety of those living or working near the water will depend on their presence of mind, says Civil Defence. But they will have no way of knowing whether the quake has occurred under land or sea. The best advice is probably to move well above water regardless.

Meanwhile, it is little comfort to Chile that it did not have to deal with a tsunami as well. That country, New Zealand's partner in a Pacific trade pact and similar to us in its resources and recent economic policies, is coping with its second megaquake in 50 years.

Lessons learned from the 1960 disaster are said to have reduced the death and destruction this time, but by last night the toll was more than 700 dead and the infrastructure destruction was extensive.

Chile's Government says it can cope; it has declined foreign aid. Other countries can only maintain the offer of assistance, check their civil defences and wonder how they would measure up to the same disaster.