Widespread disruption from strong earthquake

The destructive earthquake which hit Christchurch early today has caused widespread communications and travel disruptions.

Much of the South Island's rail network was closed after the 7.1 magnitude earthquake hit at 4.35am.

A 5km stretch of rail track near Kaiapoi was damaged and KiwiRail said there was less extensive track damage near Belfast and at Rolleston.

None of KiwiRail's 15 trains operating on South Island rail lines derailed when the earthquake struck.

Rail lines north of Kaikoura and south of Dunedin reopened at 10.30am.

The Lyttelton tunnel has been inspected and declared safe and KiwiRail said there appears to be no track damage in central Christchurch although signals were not working because of power cuts.

Track crews were checking bridges and tunnels throughout the region for damage.

Most roads held up well, said the New Zealand Transport Agency but motorists were urged to stay off the roads unless their travel was essential.

Some state highways were damaged but only two road closures were needed because of slips and road slumps. The ground had also moved around some bridge abutments.

NZTA Canterbury state highways operations manager Peter Connors said SH77 between Methven and Windwhistle and Mid Canterbury had been closed. SH75 Taipapu to Kaituna in the Banks Peninsula area near Christchurch had also been affected but remanded open.

"Checks of key state highway structures in the region show that overall they have stood up to this quake remarkably well," said Mr Connors.

Key bridges on the SH1 over the Ashburton and Rakaia Rivers to the south of Christchurch and across the Waimakariri River north of Christchurch are operational. The Chaney's Road on ramp on to SH1 north of Christchurch is closed."

All Metro bus services in greater Christchurch were suspended for today and tomorrow and New Zealand Post said there would be no mail deliveries today.

Land line telephone services largely remained intact after the earthquake. Telecom said the network had back up power working but some small roadside cabinets had lost power and that affected phone services to customers in the immediate vicinity.

Both Telecom and Vodafone had warned people not to use the acellular network unless it was essential to avoid jamming the system as cell sites began to run out of battery power.