Christchurch has just been shaken by the biggest earthquake it's experienced in the last 12 months.

The magnitude 4.2 quake, struck at 12.24pm at a depth of 11 kilometres, 10 kilometres west of Christchurch.

Newstalk ZB reporter Scarlett Cvitanovich says the quake was felt strongly in the second floor of the Christchurch Newstalk ZB office in Middleton with the whole building "creaked violently and shook for several seconds.

The quake comes just one month out from the five year anniversary of the deadly 2011 February earthquake.