Skip to main content

Tsunami national warning

Saturday, 12 March 2011 11:00 a.m.

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.   Summary:  The Pacific Tsunami Warning Centre (PTWC) issued a Tsunami Warning for New Zealand in response to the above earthquake. Confirmation has been received that a tsunami was generated. 

Wave heights of up to 4 metres have been measured in coastal Japan.  First arrivals have been measured by coastal gauges at the New Zealand coast. At Raoul Island first arrival was recorded at 0635 hours today and at North Cape at 0710 hours. Additional arrival times have been detected for the upper North Island (see table below). Initial wave amplitudes were in the order of 15cm but with measurements of up to 40cm over the last four hours with some harbours reporting amplitudes of up to 50cm and tidal surges.

Modelling indicates that the highest wave amplitudes are expected to occur in the period from now until around 1300 hours today. The pattern of wave arrival closely matches that forecast by the modelling that has been undertaken for this event. The New Zealand Tsunami Expert Panel assessment is that there is a marine and minor land threat only for parts of the upper North Island coasts of New Zealand.

See the attached threat level map and threat zone table for further details. The Green and Blue shaded areas on the map indicate where a minor land and marine threat exists, respectively. Threat DescriptionBased 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 m) now exists in 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 arrive later and may not be the largest. The larger arrivals are 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 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 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

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 expected arrival time in the Bay of Plenty was about 7.20am.

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 still remains in place for the Bay of Plenty. 

 A wave of approximately half a metre is the most likely scenario - arriving between 8.00am and 2pm.  The marine threat affects beaches, estuaries and the sea by causing strong and unusual currents and unusual wave activity.

 The Surf Life Saving Championship organisers have been advised of this threat and will be updated every 30 mins, or as required, as more information comes to hand.

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 are staffed this morning 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: