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Warning lifted, but unusual sea conditions still possible

18 Sep 2015

An official tsunami warning in place for much of New Zealand’s east coast since yesterday has now been formally lifted, however, Northlanders are being urged to be aware of possible unusual and strong tidal conditions over the next day or so.

The Ministry of Civil Defence & Emergency Management (MCDEM) announced at 1400 hours today it was officially cancelling tsunami warnings generated after an 8.3 magnitude quake off Chile.

Northland CDEM Group spokesman Graeme MacDonald says the impacts of the tsunami had panned out largely as experts had predicted, with the first waves generated by the quake reaching New Zealand early this morning.

In Northland, the impacts had once again included strong tidal surges at Tutukaka Harbour, not unlike those which had previously affected the area and other small harbours after similar large overseas earthquakes in recent years.

Mr MacDonald says while MCDEM had now lifted its official tsunami warnings, Northlanders should be aware the quake’s effects could continue to impact on local tides and currents around the region’s east coast for another 24-36 hours.

“That’s certainly been the case in previous events where we have encountered quite strong and unusual sea conditions for some time.”

He says while the Chilean quake’s impacts on Northland had fortunately been only minor, the incident had provided a useful and timely reminder of the potential risks tsunami pose.

“However, it’s important to remember that with tsunami generated by far away events like the Chilean quake there’s typically a number of hours before there’s any impact on us; in the case of a ‘locally-generated’ tsunami, it could strike within an hour or even less.”

Mr MacDonald says the latter scenario would leave little or no time to activate official warning mechanisms, which included the region’s network of 150-plus tsunami sirens.

He says it’s important to remember Northland’s siren warning system is not designed to trigger evacuations.

“Its main purpose is actually to alert people they need to seek further information about potential tsunami risks from official sources.”

Mr MacDonald says given tsunami generated by earthquakes or volcanic activity close to New Zealand might not leave enough time to trigger official warning networks, being able to recognise natural warnings from the surrounding environment is crucial.

“Things to look out for include earthquakes (either strong with shaking ground or weak and rolling lasting a least a minute), unusual sea behaviour (including a sudden sea level fall or rise) and any loud and unusual sea noises, especially the roar of what sounds like a jet engine.”

Meanwhile, Mr MacDonald says routine testing of Northland’s tsunami network part to ensure all 150-plus sirens are working correctly will go ahead as planned on Sunday 27 September to coincide as usual with the onset of Daylight Savings.  (Sirens will sound twice – firstly at 9.20am for 10 minutes and again at 10am for just 30 seconds).

“Information about the warning system, including audio of what Northland’s tsunami sirens sound like, can be found at www.nrc.govt.nz/tsunamisirens

General information about Civil Defence generally is available from www.nrc.govt.nz/civildefence or from the Civil Defence Facebook page www.facebook.com/civildefencenorthland