The Hikurangi Subduction Zone lies off the eastern coast of New Zealand's North Island, where the Pacific Plate dives westward beneath the Australian Plate along a megathrust more than 600 kilometres long. It is the largest and potentially most dangerous fault in the country, capable of generating magnitude 8-plus earthquakes and major tsunamis.
The plate interface is locked in some sections, particularly beneath the southern North Island near Wellington, where strain accumulates for future great earthquakes. Further north the subduction zone hosts slow-slip events, quiet episodes in which the plates creep over weeks to months without violent shaking, a phenomenon intensively studied by scientists.
Although no great megathrust rupture has been instrumentally recorded, geological evidence of past uplift and tsunami deposits shows the Hikurangi zone has produced huge earthquakes in the past. It is now recognised as the dominant tsunami and earthquake threat to the east coast of the North Island.