Explosions designed to simulate earthquakes and help develop ground-repair techniques will start again at Queen Elizabeth II Stadium this week - to the chagrin of some residents.
The Earthquake Commission (EQC) will start the tests tomorrow, detonating up to 25 explosive charges at depths of up to 12 metres.
Residents would be warned by a siren sounding five minutes before a charge and again one minute before.
EQC Canterbury events manager Reid Stiven said the tests would build on those done by the Building and Housing Department in November to aid foundation design.
"[They] provided good results, particularly for a method involving stabilisation of a 2m layer beneath the building platform.
"These tests are designed to assess some variations to this method and will provide information that will assist in the design of cost-effective and durable foundations for properties in [technical category 3] areas."
At the boundary of the stadium, the shaking would mirror a magnitude-4.0 quake 10 kilometres away, he said.
"The closest dwelling is about 270m from the test site, and the level of shaking experienced there will be considerably less," he said.
"The previous test created the right level of shaking, and now we need to undertake similar testing but for a slightly longer period of time. EQC's testing will therefore simulate the effects of a more distant event."
Residents across "a large area" would be informed by letter, he said.
"Some people are more sensitive to vibrations than others. However, the levels of shaking transmitted to the nearest houses will be low and there should be no risk of damage."
Parklands resident Ivor Jones said the shaking that accompanied the previous round of tests in November was "as bad as any earthquake".
"It was different. It was a sharp crack. It was almost as though it was right under our house," he said.
"I'm surprised the windows didn't shatter - and we're in Parklands."
Jones, who lives less than 1km from QE II Stadium, was not included in a mail drop to warn residents of the upcoming tests then, and had not yet received any notice this time.
"There's been no information for residents. The earthquakes are bad enough without having this man- made stuff going on," he said.