Swaying Wellington towers raise concerns as more earthquakes predicted

An engineering expert has raised concern about tall Wellington office blocks swinging and swaying last night as earthquakes hit and he predicts further seismic activity.

John Hare, the Christchurch-headquartered national chief executive of engineering specialists Holmes Group, said he was worried about structural damage to the towers and predicted more quakes possibly of magnitudes 6 and 7, but more in the magnitude 5 and 6 range.

"I'm concerned about Wellington and the tall buildings. The duration of the event has a big effect on tall buildings. The longer strong shaking goes on, the more these blocks would get a bit of a swing on.

"You could expect buildings to move 200mm to 300mm in each direction with that sort of earthquake and the amount of damage will vary between the buildings due to the type of building and its height.

"Some of the taller buildings in Wellington should be looked at closely because they gradually build up momentum. It's like pushing a kid on a swing. The building is rigid but the more it moves, the greater the stress being put on the joints. We could see more severe damage. We'll be checking stairwells, lift wells, support walls, ceiling spaces and joints between all the beams and columns," said Hare who was the former technical director of Holmes but took leave to become principal engineering advisor at the Canterbury Earthquake Recovery Authority in 2011 for two years.

In 2013 he won an Institution of Professional Engineers New Zealand award and has held senior leadership and governance roles within Holmes, as well as sitting on a number of advisory boards and committees.

Staff at NZX listed Precinct Properties are now checking Wellington buildings in their $1.5 billion portfolio.

Scott Pritchard, Precinct chief executive, said damage had already been discovered to two tall blocks on The Terrace. Engineers from Holmes would be engaged to check all Precinct's Wellington buildings, Pritchard said.