Marlborough Mayor John Leggett says property damage appears to be more widely dispersed across the district than during the previous Seddon earthquakes.
But it is still too soon to get an accurate picture of the destruction, he said.
"Our civil defence volunteers, fire crews and Red Cross teams are out there now, making their way around the areas we believe to be worst affected," Leggett said.
"We know there has been significant damage and many people will be feeling very stressed because aftershocks are continuing and that may go on for a while yet."
Leggett spent the first five hours after the midnight earthquake at Marlborough's emergency headquarters in Blenheim.
He is urging the community to help each other wherever possible.
There has been damage across Blenheim but there has been no assessments to its extent yet.
Marlborough Civil Defence Controller Richard McNamara says fire crews are doing rapid assessments and more help is being recruited to assist, including defence staff from the Department of Conservation and RNZAF Base Woodbourne.
Crews will be going door to door to assess damage and to offer assistance where required.
NZ Transport Agency said there had been significant damage on the east coast north of Goose Bay to Seddon.
Bridges north of Blenheim across the Wairau River have been damaged and are closed.
Shipping channels into Picton are closed as are the ferry terminals in Wellington and Picton.
Welfare centres are open at Tuamarina, Waikawa Marae and at Ward.
People have been allowed to return to their homes since the tsunami alert was downgraded.
Civil Defence urges people to take care of themselves and their families, check on the neighbours, do not travel unnecessarily, and listen to the radio for updates.
"Fortunately our rural communities are resilient and I am confident that people will support each other," Leggett said.
"Our civil defence response swung into action immediately; we have planes and helicopters in the air and we'll get more information as the day progresses."