Wellington's CentrePort has suspended operations until further notice as it deals with damage to its buildings and liquefaction from last night's 7.5 magnitude earthquake.

The capital's port authority is among those facing disruptions after the quake, centred near Hanmer Springs in the Hurunui district, with port companies in Napier, Timaru and Christchurch also dealing with the fallout of the natural disaster that disrupted rail and ferry services across the country and shut down the capital's CBD. The Ministry of Civil Defence and Emergency Management has narrowed its tsunami marine and beach threat to between Wellington to Banks Peninsula.

"We have sustained damage to buildings and the port and also some liquefaction and differential settlement in places," CentrePort chief executive Derek Nind said in a statement. CentrePort was working through a process with tenants to ensure all buildings were safe before they were re-occupied, which would happen over the coming days, he said.

Christchurch's Lyttelton Port Co, which embarked on a long-term redevelopment plan after the 2011 earthquakes, has re-opened some operations, receiving and delivering freight and cargo including logs and cars, and hasn't found any major concerns in its inspections so far, it said in a statement on its website.

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"The railway line south of Christchurch is open, as is the Rolleston to Christchurch route. However, the Christchurch to Port route remains closed and we are awaiting further updates from KiwiRail," it said.

Napier Port closed while the tsunami warning was in place, and the sole boat in port, a fishing vessel, was sent out to the harbour, a spokeswoman said in an emailed statement.

"Operations resumed early this morning and we are monitoring the wave activity closely," she said. "Our engineers are undertaking a full assessment of our infrastructure, including hydrographic surveys of the inner port and shipping channel, and early indications are that the port has not sustained any damage."

PrimePort chief executive Phil Melhopt said the Timaru port "evacuated several larger ships from the port given the tsunami warning," and will let them back in "once we have inspected our infrastructure and the tidal surges subside."

Dunedin's Port of Otago said it hasn't faced any disruptions from the quake or tsunami warning, while Bluff-based South Port New Zealand wasn't immediately available for comment.