Christchurch has been shaken by two minor aftershocks today. 

The first, a magnitude 4, struck at 11.07am and was centred 10km southwest of Christchurch at a depth of 12km. 

Social media users described the shake as "sneaky", "agressive" and "a cheeky little number".

Then at 9.26pm a "grunty", "noisy" magnitude 3.9 quake struck. It was centred 10km east of Christchurch at a depth of 5km. 

There were no reports of damage or injury.