Rather than a magnitude 6 aftershock centred several tens of kilometres west of the city on the recently revealed Greendale Fault, the fault rupture was almost under the city, about 5km below the Heathcote to Lyttelton road tunnel in hard volcanic rock that snapped violently at 12.51pm that day. The angle of the previously unknown fault under the Port Hills directed the energy released by the earthquake straight back at the city, with severe shaking in eastern parts of Christchurch.
Richard Cosgrove/Stuff
Eighteen people died in the PGC building on Cambridge Tce after the February 2011 earthquake struck Christchurch. Those ground motions had been thought to be among the most extreme in the world to date.