A magnitude 8.1 earthquake struck near the Kermadec Islands on Wednesday morning, triggering a widespread tsunami alert throughout the country.
This was the scenario facing staff at Whanganui Hospital during Operation Tangaroa, a nationwide exercise which tested the country's readiness for, and reaction to, the impact of a tsumani.
Civil Defence, councils and district health boards throughout the country took part in the exercise.
"We are anticipating potentially hundreds of casualties, but we don't yet know how the hospital itself will be affected," said Simon Ward, the Whanganui District Health Board's emergency manager said.
He said the call came from the Ministry of Health about 9.20am on Wednesday, and the hospital's emergency operations centre [EOC] immediately swung into action under a code red - the highest alert rating.