In the dust and daze, people saw bits of buildings give way and stone and masonry topple. They knew they had to get out of there, and they had to know what had happened to loved ones.
Cellphone networks were instantly overloaded with calls not only within the city but, soon, from family in other parts of the country as the news spread. A Herald team of reporters reached the city by evening.
Staff on APN's Christchurch paper, The Star, set up a temporary office in the western suburbs and continued to bring out the paper with help from the Herald in Auckland.
The quake was much worse than any of the aftershocks that had shaken Christchurch since the magnitude 7 earthquake five months before. This one, geologists reported, was magnitude 6 but shallower than the original and closer to the city.
The ruptured fault under the Port Hills had generated ground forces unprecedented in New Zealand. Vertical acceleration 1.8 times gravity was far more than stone walls could survive.
People stumbling through the Square that day saw the distinctive Cathedral spire had gone, reduced to a pile of dusty rock.
Other colonial churches were in ruin, as was the Provincial Council Chamber and the popular Arts Centre precinct.
But those living in the eastern suburbs had a more urgent problem when they reached their homes. The shaking had caused ground water to come to the surface, covering paths and driveways in the stinking muck of "liquefaction".
Next day a student volunteer army arrived to help begin the task of shovelling it away.
For some people in the east, living close to the river or the estuary where the land had subsided towards the water, there was no way to save their buckled homes or rebuild on the same land. These "red zoned" households received a Government pay-out. Many in the "green zone" were left to argue with their insurers for repair or replacement.
Not much could be decided while the quakes continued. Two more magnitude 6 aftershocks hit the city in 2011.
But mid-way through 2012 a plan was drawn to give Christchurch a new heart.
What are your memories of the 2011 Christchurch earthquake? Leave your comments below