Tsunami sirens few and far between and mobile alerts don't reach everyone

A combination mobile-phone alerts and sirens areas will alert Aucklanders to an approaching tsunami but residents are urged to not wait for a warning if they experience a strong earthquake.

Only the Rodney and Waitakere areas have sirens and mobile alerts do not always get through.

In 2020, two sirens were installed in Orewa in addition to the mobile-phone emergency alerts that smartphone users receive.

There are no tsunami sirens installed on the North Shore, meaning suburbs in the East Coast Bays area, like Browns Bay, are reliant on cellphone alerts and other methods of warning residents.

Is Auckland as ready as it could be? Image: Flikr, Gadfiu; CC BY 2.0

Most tsunami risk experts agree that relying on one form of alert is not ideal, and a combination is better.

NIWA hydrodynamic scientist, Dr Emily Lane, says tsunami sirens are not as obvious as they sound.

"It is not as simple as just installing them and then everything is fine,” she says.

“While sirens are a universal warning system, there have been situations where the tsunami signal in one location was the ‘all clear’ signal [in another],” Dr Lane says.

To minimise confusion and complacency among coastal residents, Dr Lane says that ultimately people need to follow the "Long or strong? Get Gone!” response after an earthquake.

This is in recognition that newer technology, like mobile emergency alerts, cannot reach everyone.

John Watson, from Auckland Council, says sirens are a universal warning system that people recognise and together the two-alert combination provides a reliable system.

"Phones are a useful tool of course but they should not be relied on in isolation.

“There are occasions especially at a beach where people may be swimming or doing an activity where it's not possible to have their phone on them,” he says.

For these reasons, people living in areas without sirens that are at risk from inundation in a tsunami, to act immediately following a large earthquake without waiting for an official warning.

Regular tests take place of both the tsunami sirens and the mobile-phone emergency alerts.