Saturday, March 12, 2011

Update - from Update 11

Apologies for the gap


The Pacific Tsunami Warning Centre (PTWC) has 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. Wave heights of 0.2 m have been observed in Nauru and Honiara.

The New ZealandTsunami 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.

Based on real-time tsunami modelling and comparison with historical events, the interpretation is that a minor land threat (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 (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 to Gisborne. Unusual tidal surges may be observed in other parts of the country.

As at time of issue of this update (#11), passage of the wave through the South Pacific has been observed, however there is no indication of wave arrival in the Kermadec islands. Wave heights observed in the Pacific islands confirm the current threat assessment for New Zealand.

The first wave to arrive to New Zealand was calculated to be in the area around North Cape at approximately 0623NZDT 12 March 2011. Monitoring of the propagation of the tsunami across the Pacific indicates that actual arrival times may be an hour later or more than the modelled times published (previously).

A tsunami is a series of waves or surges and the first wave may arrive later and may not be the largest. The largest arrivals are anticipated from about 0800 NZDT and expected to last for several (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. Local civil defence authorities may supplement these messages by applying local threat assessments.

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.

MCDEM and scientific advisors are closely monitoring the situation to determine the severity of the threat to New Zealand.

This warning has been issued to all local civil defence authorities, emergency services, other agencies and media.

No comments: