A magnitude-3.8 earthquake struck near Akaroa this afternoon.
GeoNet said the quake hit at 3.43pm, 30 kilometres west of Akaroa at a depth of 17km.
The quake's intensity was described as "moderate".
More than 220 people have reported feeling the quake on the GeoNet website.
A 3.1 quake struck about 20 minutes later.
It hit 35km west of Akaroa at a depth of 18km.
GNS Science duty seismologist Anna Kaiser said the location of the first quake offshore south of Lake Ellesmere was worth noting.
"It does seem to be in a slightly different location, where we haven't been having them."
It was too early to judge its significance, she said.
At 17km deep it was "towards the deeper end of what we've been seeing".
Seismologists were aware of faults in that area.
There was a quake of about 5.5 near Lake Ellesmere in 1870.
- The Press