Macquarie fault zone

The 1,600 kilometres (990 mi) long Macquarie fault zone (also known as the Macquarie Ridge, its gazetted name since 2015, the Macquarie Ridge complex or historically as the Macquarie Fault) is a major right lateral-moving transform fault along the seafloor of the south Pacific Ocean which runs from New Zealand southwestward towards the Macquarie triple junction. It is also the tectonic plate boundary between the Australian plate to the northwest and the Pacific plate to the southeast. As such it is a region of high seismic activity and recorded the largest strike-slip event on record up to 23 May 1989, of at least Mw 8.0

Geography

The Macquarie fault zone extends south of New Zealand on the South Pacific Ocean's seafloor except where it surfaces as Macquarie Island. Some of it is on Tasman Sea sea floor, north of the line between the south of the Auckland Islands and Tasmania. To its west on the sea floor is the South East Tasman Basin and to its east the Solander Trough and Emerald Basin. Technically the plate boundary becomes part of the Emerald fracture zone to the south of the Hjort Trench, so the zone does not quite reach the Macquarie triple junction.

Geology

The Macquarie fault zone term is also used often now to refer to a major central part of the plate convergent structures south of New Zealand that has become to be termed the Macquarie Ridge complex as the geology has been better characterised. The northern part of this complex is an extension of New Zealand's Alpine Fault which becomes the Puysegur Trench and ridge to its east. New Zealand is continental crust and the northern parts of the complex are associated with oceanic crust subducting under the continental crust of Zealandia. This north Macquarie Ridge Complex has to its west the Resolution Ridge which separates the oceanic crust of the north and south Tasman basins and defines the western margin of the Macqurie Block.