New Zealand is a very active seismic and volcanic region of the Pacific Ring of Fire, on the boundary of the Australian and Pacific Plates; however, there is a difference between the 2 islands: volcanoes and earthquakes on the North Island and earthquakes only on the South Island (see maps below):
Location of New Zealand volcanoes
New Zealand Earthquake Map
What are the tectonic features that account for the difference between the North and South Islands?
Additionally, how will this boundary develop in the future