Repair crews are working around the clock to get the Port of Lyttelton operational again.
The port's coal-loading facility and container terminal were particularly hard hit by Monday's quakes.
The port's chief executive, Peter Davie, says it is unable to load or unload container ships, and it could be Friday before the backlog of vessels can begin to be cleared.
Mr Davie says new cracks have appeared in areas paved since the February earthquake.
Cranes are being put back on rails, and repair work is also being done under the wharves, he says, as crews work flat out, round the clock.
Mr Davie says rail operations in and out of the port are running as usual, and the oil berth should be operating by the time the next tanker arrives on Monday.