Christchurch's 45 tsunami warning sirens may be upgraded as the noise they make does not comply with the national standard.
The Christchurch City Council is looking at options to make them compliant with the national standard.
The council installed the sirens, which are located along the coastline between Brooklands and Taylors Mistake, in two stages between 2012 and 2014.
The sirens are regularly tested to ensure they are working properly however, the noise they make does not comply with the tone set in the National Emergency Management Agency's (NEMA's) Technical Standard.
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"Our sirens don't comply with two of components of the technical standard but they are still an effective tool that we can use to alert people near the coast that a tsunami might be coming,'' said council head of civil defence emergency management Rob Orchard.
"The sirens though are only one of the tools we would use if a tsunami was coming our way."
Orchard said he is investigating how the sirens could be upgraded so they comply with NEMA's Technical Standard.
He will bring a report back to the Sustainability and Community Resilience Committee with his findings.
"If you hear the tsunami sirens, check if there is an official tsunami warning for your zone. The warning is given on the radio, television, social media or through an Emergency Mobile Alert to your phone.
"If there is a local source tsunami, we will not have time to activate the sirens. In that case, the best warning sign is the earthquake itself. "
If you are near the coast and you experience a strong earthquake that is difficult to stand up in, or lasts for a minute or more, you should immediately move to higher ground or as far inland as possible.