A magnitude 4 earthquake is to strike Christchurch this morning - but this one will be man-made.

The "earthquake" is to strike at 11.30am, at QEII Stadium, at a depth of up to 12km.

The jolt is part of tests by the Earthquake commission into whether liquefaction-prone land in the east of the city can be repaired.

About 25 small underground explosives are to be placed up to 12 metres deep and set off to simulate an earthquake of about magnitude 4.


EQC Canterbury events manager Reid Stiven told Radio New Zealand the shaking from the earthquake will go on for about 10 seconds, and will be felt up to 10km away from the site.

"People have no reason to fear further damage or on-going explosions," Mr Stiven said.

Sirens will sound five minutes and one minute before the explosions are set off at 11.30.

"People within 10km of QEII may feel a very minor shaking, but we are very confident they won't see any damage from it."

Today's test follow ones undertaken by the Department of Housing in November last year.

Mr Stiven said a report into the possibility of repairing the land should be completed within about eight weeks.