The 5.3 magnitude quake rocked the region at 10.34pm and was folowed by a further 10 aftershocks overnight, with the biggest being a magnitude 4.4 shortly before 3.30am.
A Halswell New World staff member said "everything fell off every shelf". The store lost "an extensive amount of stock" with wine and juice bottles smashed in the aisles.
About a dozen staff came in to clean up the mess for four hours last night.
The main jolt was first thought to be centred 10km west of Akaroa, but GNS seismologist John Ristau said this morning that records now show it was centred just 10km south of Christchurch city, near Halswell.
The New World staffer, who did not want to be named, said she was not surprised to hear the earthquake centre was actually close to Halswell.
"It must have been centred near here because this is the most amount of damage we have sustained this year."
Following the midnight clean-up the supermarket opened on schedule at 7.30am today.
Mayor Bob Parker, on his Facebook page, said the city should expect a few more "tremblers".
GNS Science duty seismologist John Ristau said it appeared another small fault below Banks Peninsula had ruptured, causing the sharply felt magnitude 5.3 quake.
"You are sitting on hard volcanic rocks there and when it breaks, it tends to break very strongly, producing a lot of shaking and energy."
Another nerve sapping jolt followed by a shaky night of aftershocks and for the first time, I am not in Christchurch to feel any of them. I am away at a conference in Hamilton, up in the North Island, and although physically safer, have spent most of the night checking the news and facebook to see how they are getting on down south, and still jumping everytime the airconditioner kicks in and makes a noise. Habits that don't go away!
Thinking of everyone...
Hoping to get home on Friday, if the volcanic ash doesn't drop lower and disrupt the domestic flights more than it already is today...