A shallow 4.5-magnitude earthquake struck Christchurch on Tuesday night.

The quake, centred 10km southwest of the city at a depth of 11km, hit at 11.30pm and was felt across Christchurch, according to GNS Science GeoNet Data Centre.

It was originally measured as a "strong" magnitude-five quake but this was downgraded.

A deep 4.6-magnitude quake also hit 10km south of Havelock, Marlborough, at a depth of 70km about the same time.