Geology of New Zealand - Earthquakes

Earthquakes

Deep earthquakes originate in the subducted plate. Because the Pacific Plate is subducting under the eastern side of the North Island, there are frequent deep earthquakes east of a line from the Bay of Plenty to Nelson (the approximate edge of the subducted plate), with the earthquakes being deeper to the west, and shallower to the east. Because the Australian Plate is subducting under the Pacific Plate in Fiordland, there are frequent deep earthquakes near Fiordland, with the earthquakes being deeper to the east and shallower near the west. There are few deep earthquakes along the Southern Alps, because the two sides largely slide past each other.

Shallow earthquakes are caused by stresses in the top plate. Shallow earthquakes are more widespread, occurring almost everywhere throughout New Zealand (especially the Bay of Plenty, East Cape to Marlborough, and Alpine Fault). However, Northland, Waikato, and Otago are very stable. Canterbury had been very stable until the 7.1 Canterbury Earthquake on 4 September 2010. In the first three weeks following that quake, there were more than 1000 aftershocks in the region.

A Map showing the distribution of earthquakes in New Zealand can be obtained from Te Ara Encyclopedia of New Zealand. Current earthquake and volcanic activity can be obtained from the GeoNet website.