The quake was unlikely to cause anything more than minor damage, Mr Reyners said.
Many Christchurch residents reported feeling the quake strongly.
Desere Girdlestone said: "Thought King Kong was shaking my car."
Sel Leigh said: "Nothing like a fresh [earthquake] to send the oldies at work into a panic. Moving cars, jackets on, car keys at ready for "the next one in an hour"
The quake was followed by a 3.8 magnitude aftershock at 1:55pm.
It struck 20km east of Christchurch at a depth of 10km.