An earthquake has hit Christchurch, with residents reporting a "significant shake".

The quake hit at 8.43am, with initial reports from Geonet saying it measured magnitude 3.9 and 7km deep. It was centred about 5km south-west of Christchurch. About 2500 people have reported feeling the quake, with light to moderate shaking.

People as far north as Opotiki and Taranaki reported feeling it.

It's the second significant quake in the city in two days. A shallow magnitude 3.5, 6km deep quake just after midnight on Sunday morning was felt across Christchurch with over 4000 people reporting feeling the quake.

Alison Is in Ilam told Chris Lynch she could hear the quake coming.

"Compared to the one on Saturday night, it was much stronger. It was a nasty one."

She says the timing of it isn't great.

"It's mean of them to have it today. I thought we won the netball, and those people in Northwood, why do they have to give one of these at this stage?"

Caller Robyn says her house doesn't usually shake unless the quake is more than a magnitude four.

"It wasn't a jolt or anything, the whole house started to shake. Things were rattling in the cupboard, so I spun round and had my hand on the door handle, ready to leap out to the driveway."

A shaky start to the week for Christchurch with a M3.9 quake, 7km depth. Over 4000 of you reported feeling that one. Just another reminder that the Christchurch aftershock sequence is still ongoing. Take care #eqnz pic.twitter.com/0cOdpGxTh5

— GeoNet (@geonet) July 21, 2019