23 Jul 2012

Tsunami sirens difficult to hear, residents say

7:19 am on 23 July 2012

Christchurch's half million-dollar tsunami sirens came through their first trial run in a less than convincing fashion, failing to be heard by many of those living close to the sea.

Twenty-two sirens have been installed by the Christchurch City Council to warn those living within 500 metres of the coast to move to higher ground in case of a tsunami.

The sirens were supposed to be audible from Waimairi Beach to Sumner.

Some residents in Sumner told Radio New Zealand the sirens were weak and difficult to hear.

Christchurch civil defence manager Murray Sinclair acknowledges problems with the reach of the sirens' sound.

Mr Sinclair says the 22 sirens installed so far are just the first phase of a possible 79 which could eventually cover the region, including some set further back from the coast.

But he says the extra $1.4 million cost may be hard to justify given other council spending priorities following the earthquakes.

Christchurch mayor Bob Parker says the sirens are designed to warn of tsunamis generated by earthquakes thousands of kilometres away, such as in South America, for which there would be plenty of notice.

Mr Parker says deep water and signficiant vertical displacement during an earthquake is needed to create a large tsunami. Those occuring under the sea closer to New Zealand would cause small wave patterns.

"In the immediate bay area you're very unlikely to get anything over a metre," he says.

No decision has yet been taken on whether to buy the additional sirens.

The online survey has been set up to get people's feedback so changes can be made. A report will be presented to the council at the end of August.