A practice emergency response to a rupture along the Alpine Fault is being described as one of the most comprehensive tests of its kind in the world.
All Civil Defence emergency management groups in the South Island were tested to see how they would cope if a magnitude-8 earthquake hit the West Coast.
University of Canterbury PhD student Tom Robinson designed the scenario and said the fictional quake struck early on Wednesday.
As the scenario unfolded, there were lots of aftershocks and two major tremors hit the West Coast and Dunedin area on the eastern side of the island.
With landslides blocking all the big gorges for the exercise, Queenstown and the West Coast were completely cut off.
Mr Robinson said the test is one of the first in the world to take into account geomorphic effects, such as landslides, liquefaction and rockfalls.
The test response was co-ordinated in Christchurch and ends at 9pm on Wednesday.