Tsunami risk to Christchurch
15 March 2011, 8:30pm
The known risk to Christchurch from a tsunami has not changed since the 4 September 2010 and 22 February 2011 earthquakes.
Civil Defence has received a number of inquiries around tsunami risk, following the events off Sendai, Japan.
The Christchurch coastal evacuation plan remains in place and would be implemented as normal for tsunami from a distant source, if necessary.
The small aftershocks experienced in Canterbury over recent months are not big enough to generate tsunami.
If a larger earthquake were to occur offshore in the Canterbury region, any resulting tsunami would be small in size and not expected to inundate land.
Most tsunami hazard in the Canterbury region originates from South America. The travel time for these tsunami is approximately 12-14 hours which allows time to evacuate coastal areas like Southshore.
As for anywhere in New Zealand, no warning could be issued for a near source tsunami as the travel time is too short to implement an effective evacuation procedure. For tsunami originating from local sources, observation and preparedness are key to public safety.
If you are on the beach during an aftershock and feel strong shaking for more than 20 seconds, or observe unusual tidal behaviours you should leave the beach immediately, go to higher ground and wait for further advice from emergency services.
People living east of the Ferrymead bridge (Sumner, Redcliffs, McCormacks Bay) should go up their nearest hill in such an event. The Bridge St bridge, South Brighton, is functional as are all key bridges across the Avon and Heathcote rivers.