A magnitude 4.7 earthquake has rocked Christchurch this afternoon, only hours after a swarm of more than 70 quakes hit Bay of Plenty overnight.

GeoNet said the quake happened about 1.42pm 20km northwest of Akaroa. At a depth of 5km it caused light shaking.

There was also a series of lighter quakes in the area about 30 minutes prior at magnitudes 4.2, 2.6 and 2.7, with light to moderate shaking.

Nearly 7000 felt reports have been recorded by GeoNet from the 4.7 shake. It said on Twitter the quake was "felt throughout the city, Port Hills and further inland".

Most of the felt reports were of weak to light shaking.