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Home > Latest News > Media Releases > Media Releases 2011 > March 2011 > Tsunami threat to New Zealand

Tsunami threat to New Zealand

Saturday, 12 March 2011 5:00 p.m.

Release # 16

A tsunami marine warning is in effect for New Zealand:
The tsunami warning will remain in effect until a cancellation message is issued by MCDEM.

An earthquake has occurred with these parameters:

Origin time:

0545Z 11 March 2011

NZ time:

1846NZDT 11 March 2011


38.2 North 142.5 East




Near East Coast of Honshu, Japan



The above magnitude is provisional and may be increased or decreased as more seismic data becomes available.  


The Pacific Tsunami Warning Centre (PTWC) issued a Tsunami Warning for New Zealand in response to the earthquake off the east coast of Honshu, Japan. Tsunami wave heights of up to 4 metres have been measured in coastal Japan. Smaller tsunami waves have reached coastal areas across the Pacific.  

The arrival of waves has been tracked by the tidal gauges at the New Zealand coast. For locations on the North Island, tsunami waves of amplitudes of up to 70cm continue to be recorded. There have also been reports of some significant tidal fluctuations. The Chatham Islands has recorded sea level changes of in excess of 1 metre. Modelling of this event suggests that the amplitude of the waves should now begin to decrease. MCDEM and scientific advisors are closely monitoring the situation and will be reviewing the level of threat over the next couple of hours. 

The New Zealand Tsunami Expert Panel assessment is that there remains a marine and minor land threat only for parts of the upper North Island coasts of New Zealand. See the attached threat level map for further details. The Green and Blue shaded areas on the map indicate where a minor land and marine threat exists, respectively. 

Threat Description:
Based on real-time tsunami modelling and comparison with historical events, the interpretation is that a minor land threat (Green on the attached threat level map i.e. wave heights just over 1 metre) for Northland between Ahipara and the Karikari Peninsula as well as in the Bay of Islands and the Chatham Islands. A minor land threat means there is a small potential for impacts on beaches in these areas. 

A marine threat (Blue on the attached threat level map, i.e. threat to the coastal marine area and small boats) remains in place for the northern North Island from Kaipara to Ahipara and south of the Karikari Peninsula, around Coromandel Peninsula and Bay of Plenty to Gisborne. 

Coastal areas not shaded (white on the map) are under no tsunami threat, however, unusual tidal surges may be observed and caution is advised. 

A tsunami is a series of waves or surges and the first wave may not be the largest. The larger arrivals were anticipated from about 0800 NZDT and expected to last for at least five hours. Tsunami activity such as unusual currents and changes in sea-level will also continue for several hours after first arrivals. Tsunami wave heights cannot be accurately predicted and can vary significantly along a coast due to local effects.  

Only messages issued by MCDEM represent the official warning status for New Zealand. 

The next update will be issued at 1730 hours (instead of the hourly update that has been previously provided).   

The approximate actual arrival times of detectable waves at North Island coastal gauges are as follows:


Actual Arrival Time

Chatham Islands

0900NZDT 12 March 2011

North Cape

0710NZDT 12 March 2011

Great Barrier Island

0740NZDT 12 March 2011


0750NZDT 12 March 2011

East Cape

0740NZDT 12 March 2011


0810NZDT 12 March 2011


0920NZDT 12 March 2011 (Note: low amplitude detected of less than 10cm)


0830NZDT 12 March 2011

NCMC status: 

The National Crisis Management Centre (NCMC) is activated. 

General enquiries

(04) 494 6900

Media enquiries

(04) 494 6951


Satellite phone

00881 621 465 606

HF radio call sign


Useful websites:


Bay of Plenty Civil Defence Emergency Management Group information

Bay of Plenty Civil Defence Emergency Management Group has activated and is monitoring the situation. The Whakatāne River Bar is now open.

For more media information please contact Linda Thompson, Public Information Manager 021 923 339

Update for Tauranga and Western Bay

A marine threat remains in place for the Bay of Plenty. 

Boating activities can be hazardous in these situations and so recreational and fishing boats, in particular, are advised not to be undertaken until the threat is lifted.

All boat ramps have been staffed today to advise people of the warnings.

People in coastal areas should:

1. Stay off beaches

2. Stay out of the water (sea, rivers and estuaries, including boating activities)

3. Do not go sightseeing

4. Share this information with family, neighbours and friends

5. Listen to the radio and/or TV for updates

6. Follow instructions of your local Civil Defence authorities.



Alison Clifford

Public Information Manager

021 225 5782 

Useful websites: