Christchurch was rattled by a magnitude 4.0 earthquake this morning.

GNS Science said the 12-kilometre-deep quake struck 10km southwest of the city at 11.07am.

Twitter users described the quake as noisy, with one describing it as a "big booming wobble".

Another tweeted they thought it was the start of last February's quake "all over again".


A police southern communications spokesman said there had been no reports of damage.

The quake was followed almost an hour later by a magnitude 3.0 shake.

The 7km deep quake struck 10km southwest of Christchurch at 12.06pm.