New
Zealand's position on the boundary of the Australian and Pacific plates
is the reason for the large number of earthquakes we witness. Underneath
New Zealand these two huge plates are grinding together in three distinct
ways.
To the east of the North Island the Pacific plate is being forced under
the Australian plate. Under the South Island the two plates push past
each other sideways, and to the south of New Zealand the Australian plate
is being forced under the Pacific plate.
The Institute of Geological & Nuclear Sciences records about 14,000
earthquakes in and around New Zealand each year. Most are small, but between
100 and 150 are big enough to be felt. The Institute records these earthquakes
on a nationwide network of instruments called seismographs.