No, you weren't dreaming it this morning. According to GeoNet, there really was an earthquake.
The following earthquake has been recorded by GNS:
Reference number: 3577477/G
Universal Time: 2011/09/11 17:30:35
Local time (NZST): 05:30 AM on Monday 12 September 2011
Latitude, Longitude: 41.79S, 174.58E
NZ Map Grid (E, N): 2642000, 5935000
NZ Trans Merc (E, N): 1732000, 5373000
Location: 60 km south of Wellington
Focal depth: 33
Web page: http://www.geonet.org.nz/earthquake/quakes/3577477g.html
Web service: http://www.geonet.org.nz/services/quake/3577477g
May have been felt in lower North Island and upper South Island.